When _____ different cultures, we often pay attention only to the differences without noticing the similarities.
| A．compared | B．being compared | C．comparing | D．having compared |
When he was alive, the old scientist used to say that knowledge ＿＿from practice and he gained his experience by doing a lot of practical work.
| A．was coming | B．had come | C．comes | D．would come |
He ＿＿articles for our wall-newspaper these three years, and he ＿＿about forty articles.
| A．has been writing； has written | B．has been writing； wrote |
| C．is writing； has been writing | D．has written； has written |
The children ＿＿very quiet；I wonder what they ＿＿up to.
| A．were； are being | B．are being；are | C．are；do | D．are being；do |
Jim talked for about half an hour yesterday. Never＿＿ him talk so much.
| A．I heard | B．did I hear | C．I had heard | D．had I heard |
— ＿＿ Betty this morning?
— Not yet, but she is sure to be here before noon.
| A．Have you seen | B．Will you see | C．Do you see | D．Did you see |