This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'If rubella occurs in 9-10 weeks of pregnancy what is the chance of transmission to the fetus - \nSelect and explain. \nA. 85%, B. 20%, C. 30%, D. 40%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: *first trimester is most disastrous for foetus as the organs are developing *infection during this period results in abnormalities in infants in 85% *in second trimester,detectable defects are found in 16%of infants *after 20 weeks,bih defects are uncommon (park,edition 23,page 151)', 'role': 'assistant'}]