221. There are 5 ________ in the passage about nanometer(纳米) technology we have just read. Please tell me the general meaning of the first one.
| A．persons | B．paragraphs | C．articles | D．Units |
____ he was in poor health, he worked just as hard as everyone else.
| A．But | B．Although | C．Even if | D．If |
We arrived at the station ____ the train had left.
| A．after | B．before | C．since | D．when |
___he daydreamed, Peter saw figures in the sky.
| A．Until | B．Since | C．While | D．During |
____ to New York, her father has not heard from her.
| A．Because she went | B．After she went | C．When she went | D．Since she went |
It looks ____ it's going to rain.
| A．that | B．as | C．as if | D．like that |