I just don't understand_____________ that prevents so many Americans from being as happy as one might expect.
| A．why it does | B．what it does |
| C．what it is | D．why it is |
You did me a huge favor. However, I lack words_________to express my thanks.
| A．through which | B．with which | C．where | D．for which |
Tom was running out of time in the exam, but there still remained several questions_________.
A. to be answered B. to answerC. answered D answering
If you need any more paper, I'll bring you_________.
| A．one | B．ones | C．some | D．it |
An economist is____________expert who will know tomorrow why_________things he predicted yesterday didn't happen.
| A．the; \ | B．the; the | C．an; the | D．an; \ |
Having said goodbye to their friends, they ______________for home.
|