Millions of people watched that first moon landing on television, their hearts in their mouths, aware of how difficult and dangerous an adventure it was, and what risks had to be ____.
| A．taken | B．take | C．to take | D．taking |
On________ second thought, I decided to give him________ second choice.
| A．a ; a | B．a ; the | C．the ; a | D．the ; the |
“39 Steps”is one of the most exciting films_________ directed by my brother.
| A．which were | B．which was | C．that was | D．that were |
----Have you finished the book ?
----No, I’ve read up to _______ the children discover the secret cave. .
| A．which | B．what | C．that | D．where |
Living in the central American desert has its problems, ________ obtaining water is not the least .
| A．of which | B．for what | C．as | D．whose |
---Alice, why didn’t you come the other day ? .
---I______, but I had an unexpected visitor.
| A．had | B．would | C．was going | D．did |