If you _____ smoke, please go outside because this is a non-smoking office.
| A．must | B．should | C．can | D．may |
---Excuse me, I want to have a letter mailed, but I can’t find a post office.
--- I know ______ nearby. Come on, I’ll show you.
| A．it | B．one | C．that | D．another |
---Jack failed the driving test again．
---The question is_____ we can help him avoid making the same mistake．
| A．how | B．why | C．what | D．whom |
The world is full of wonders, _____ we open our eyes to see them．
A． if only B． as if C even if D． only if
It was not until midnight ______ they reached the camp site.
| A．that | B．when | C．while | D．as |
The first decade of the 21st century ______ breathtaking, non-stop development in China．
| A．witnesses | B．witnessed |
| C．will witness | D．had witnessed |