—When did your brother begin to show his interest in medicine.—It was a Saturday _____ he noticed his classmate experimenting on a frog in the lab.
Wang Ping hesitated for ___ before he ___ to the question.
--Hello, May I speak to Mr. Wang, please? ----______
They are ___ the same size. You can take ___ half of the bread.
The book ___ three yuan, but it only ___ me two yuan.
The building is ___.