单项选择题
The （）from childhood to adulthood is always a critical time for everybody.
A．conversion B．transition C．turnover D．transformation
单项选择题 If you want this painkiller, you'll have to ask the doctor for a （）
单项选择题 The passage tells us that proof of life on Mars would （）
单项选择题 By saying "With Mars the scientific stakes are arguably higher than they have ever been" ( Line 1, Para. 4 ), the author means that （）
