1、C
He will write to you as soon as he （gets） there
这里是一般现在时表将来
2、B
3、beginning
At the _beginning__(begin) of the class,he told us a funny story
At the beginning of短语,意思是在——的开始
4、Traffic became more and more crowded, so everyone should obey the traffic rules
5、more and more 越来越
例句：It rained more and more heavily. 雨下得越来越大了.
She went farther and farther away. 她越走越远了.