1 . In the Ming Dynasty, the center was the Forbidden City, ________ (surround) in concentric (同心的) circles by the Inner City and Outer City. （所给词的适当形式填空）

2 . 钱学森被誉为中国航天之父， 他为新中国的航天事业奉献了毕生。
Qian Xuesen, ___________ __________ the “father of China’s space program”, _________ ___________ ___________ __________ the cause of new China’s aerospace.

3 . The most surprising thing about it, however, is that it can land anywhere: on snow, water, or even on a ________ field. （根据句意填空）