A. how will it learn B. will it learn how C. it will learn how D. and it learns how
单项选择题（） his second heart attack if he hadn’t smoked He might not have.
A. Would he have had B. Would he have C. Had he had D. Were he to have
单项选择题I was held up by the traffic jam, otherwise I （） here 50 minutes sooner.
A. would be B. ought to have been C. would have been D. must have been
