根据所给句子的意思，填上合适的单词，并注意其正确形式，首字母或中文已给出。

小题1:There is no indoor swimming-pool in this school and the students often go to swim o_________.

小题2:Sorry, I can’t go with you. I’m s      ______   from a serious headache.

小题3:Believe it or not, my old school friend has changed so much that I can’t r____________ him.

小题4:I can’t express how g_______________ I am for what you’ve done for me.

小题5:Although she is Chinese, she can speak English and French _________ (流利地).

小题6:Many young men ______________ (不同意) with their parents on most things because of the generation gap.

小题7:Walk two _____________（街区）, and you’ll find the super market at the corner.

小题8:Never tell him a secret, because he has got a           （松的）tongue.

我国周边安全环境面临哪些主要威胁？