udy of natural history is not something to be left to biologists. In fact, their capacity __________ the time they can spend away from their offices is very limited.

Excuse me. Do you know where the Dongying Airport is— It’s ______ the northeast of Dongying.

Someone called you just now.——I know. But I was busy at that moment. When I calledback, there was no.

It seems that living green is ________ easy andaffordable. A small step makes a big difference.

choose a new monitor (班长).