单项选择题
Taiji boxing is good ______ health, so the old man began to practise it ten years ago and now he is good ______ it.
单项选择题 The car is running ______ the speed of 120 kilometers an hour.
单项选择题 It is said that a collection of paintings by David is ______ exhibition at the Museum.
单项选择题 Students in our school often go ______ field trips.
