根据句意和汉语注释，在答题卡标有题号的横线上，写出单词的正确形式。
The teacher showed great ____________ to jump into the river to save the poor boy.  (勇气)
In the northern part of China, the lake is as ________________ as glass in winter because it isturned into ice. (光滑的)
When you try to get a good job, you will be at a big _____________ if you don’t go to a gooduniversity.（劣势）
China took action to search for the missing plane---MH370 __________ after getting the news. (立即)