在德化红酒制作的过程中，要尽量少打开容器，主要原因是为了防止（　　）

A．酒精挥发

B．杂菌污染

C．温度降低

D．空气中的氧气杀死酵母菌

They____on the program for almost one month before l was arranged to help them. Now, we____on it as no result has come out.

A．had been working: are still working

B．had worked; were still working

C．have been working; have worked

D．have worked; are still working