Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
the U.S. copyright on this publication was renewed.] Ro moved cautiously. He knew the jungles of Mars well, knew the dangers, the swift death that could come to an unwary traveler. Many easy, as the loping of Shee, the great cat. For a long moment Ro studied the approaching creatures. Then he gasped in surprise. The pursued was a young woman, a woman he knew. Na! The Ro exclaimed his surprise, then his rage. His handsome face was grim as he searched the ground with his eyes. When he found what he sought—a mouth furry face and twitching tail. The Oan, however, was too intent on his prey to notice Ro at first, and when he did, it was too late. ribs and backbone cracked under the blow. He was dead before he struck the ground. With hardly a glance at his fallen foe, Ro ran on to meet the girl. She fell into his arms and pressed her cheek to his bare shoulder. Her dark eyes were wet with gladness. Warm tears ran down Ro's arm. Finally Na lifted her beautiful head. She looked timidly at Ro, her "You're home," breathed Na. "I have traveled far to the north," answered Ro simply, "and seen many things. And now I have returned for you." "Since a long time," she answered sadly. Then she cried. And between sobs she spoke: cover of night, we were forced to leave the caves. One by one we went, and those of us who lived still travel alone." Ro groaned aloud as Na finished her tale. His homecoming was a meeting with tragedy, instead of a joyful occasion. "What of my father?" he asked hopefully. "He was a great warrior. "He had no chance to fight," Na answered. "Two of your brothers died with him on that first morning." Ro squared his shoulders and set his jaw. He wiped a hint of tears from his eyes. Na trailed behind him. Her face was grave with concern. "They are very many," she said. "Then there will be more to kill," answered Ro without turning. on a mountain peak. "You say they came from a place called Earth?" Ro asked Na in wonder. "They traveled through space in their 'ship,'" Na answered. "They called themselves an expedition." Ro was silent then. In a short time it would be dark enough to go down into the valley. When he had rescued the white ones, he would learn more about them. understood why she had crept into his dreams. The darkness settled quickly. Soon Ro could barely make out the girl's features. It was time for him to leave. He took a pouch from his waist and shook out a gold arm band. This he clasped on Na's wrist. "All men will know now that you are the mate of Ro," he whispered. And he kissed her, as was the custom of his tribe when a man took a wife. Without another word he disappeared over the edge of the cliff. They prolonged farewell. They would be together soon—on the far side of the cliff—if all went well. In his left hand and under his armpit Ro carried stones. They were of a cracked the Oan's skull like an eggshell. Ro caught the body as it fell, lowered it noiselessly to the ground. When they were ready, Ro signaled the four white people to follow him. They rose quietly and trailed him into the woods. The girl whispered something to one of the men. Ro turned and glared at her through the shadows. told them. "After a short while, we will meet Na." "Who is Na?" asked the girl. "She is the one I have chosen for my mate," Ro answered. The white girl was silent. They traveled quite a distance without communicating. Each was busy with his own thoughts. under the weight of a burden. It was a rat man, and slung across his shoulders was a girl. Ro's body tensed and quivered. A low growl issued from deep in his Ro struck his foe head on. They went down in a frenzied bundle of fury. strength, Ro tore it away before it could tighten. and lay still. Ro dismounted the limp body. His face wore a wildly triumphant expression. It changed as he remembered the girl. He ran to her side. Na was just opening her eyes. She stared around her fearfully, then smiled as she recognized Ro. The young Martian breathed a sigh of standing at the foot. The shadows were deceiving. I thought it was you. It wasn't until too late that I discovered my mistake." Ro gathered the girl in his arms. He spoke softly to her to help her forget. When she had recovered from her shock, the small group traveled on. Ro Ro smiled. and less impressive. Ro then centered his attention on the girl. Her Ro introduced himself and Na. What year is it?" "You have seen what it is like here," Ro answered. "As for 'year,' I don't understand." Ro sighed. Ro slipped his arm about Na's shoulder and drew her closer. With their heads together they slept. Ro awakened with the dawn. He was startled to find that Na had left his side. He rose quickly and strode to the mouth of the cave. Na met him at the entrance. She was returning from a clump of trees "You see," she said, "I will make you a good mate. Our table will be well provided for." "You will make no mate at all," Ro said sternly, "and there will be no table if you wander off. Your next meeting with the Oan may not be so fortunate." He glared at her for a moment, then smiled and helped her with her burden. The others in the cave awakened. Ro noticed that Charlotte had slept beside Carlson, but moved away shyly now that it was daylight. He The old man also rose. He placed a restraining hand on Ro's arm. "He's lying," said Ro with his thoughts. I have thought about it all night." Ro turned quickly. "What is it?" he demanded. Ro fell silent. He walked to the mouth of the cave and stared out. When he turned back to the others, his attention was centered on Na. He repeated his plan to the others. "But they'll kill her," gasped Charlotte. "She will be a woman alone," said Ro. "The Oan prefer to capture women when they can." Ro laughed. When they had detailed their plan, the party left the cave. Ro led them walls of the cliff rose almost straight up on both sides. "We leave you here," said Ro to the professor. "Na will lead you to the sphere. She will remain hidden until you have circled away from her. Then she will reveal herself." Ro looked at Na for a long moment before they parted. He grew very proud of what he saw. There was no fear in her eyes. Her small chin was He turned to Carlson. The young Earthman was looking at Charlotte in much the same way. "Come on," Ro said. "If we spend the rest of the morning here, the Oan over the narrowest part of the valley. If all went well, the Oan would be trapped. They would die under a hailstorm of rock. "You would have liked a more tender goodbye with Charlotte," Ro said to Carlson as they worked. "Was it fear of Grimm that prevented it?" Carlson straightened. He weighed Ro's words before answering. Finally he said, "I didn't want to make trouble. It was a bad time, and senseless, besides. Charlotte and I are planning to be married when we "Why don't you take her for your wife here on Mars? That would end the Ro seemed puzzled, then he laughed. "Last night I thought that we on Mars are backward. Now I'm not so sure. When we find our mates here, we take her. There is no one to your system, it would really be a mess. But I won't say anything. Here on Mars your kiss and a promise is probably as binding as any ceremony." Ro didn't speak. He didn't concentrate and transmit his thoughts, but kept them to himself. The pictures he'd received from Carlson were confusing. The business at hand was more grim and important than

<question>:
What became of Ro's mother?

<options>:
A She is hiding from the Oan in the cliffs.
B She was killed by the Oan.
C She was taken hostage by the Oan.
D The text doesn't tell us what happened to Ro's mother.

<answer>:

D