单项选择题
When we don't know the different ways languages are used in different cultures, we（）make serious mistakes.
A. shall B. must C. could D. should
单项选择题 Mr. Green drove slowly on the way home until he reached the high way,（）the speed limit was 60 miles per hour.
单项选择题 Our ancestors celebrated（）birth of（）child by giving away red eggs.
单项选择题 The speed at which an animal lives is determined by（）the rate at which it uses oxygen.
