This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
True about pulmonary embolism -a) ECG shows right ventricular strain patternb) PAO2-PaO2 difference in normalc) ECG also shows typical S1Q3 T3 patternd) Not a medical emergency 
Select and explain. 
A. a, B. bc, C. ad, D. ac
D: ac
Answer: D: ac 
Explanation: None