good manners to say “Sorry” when you knock into someone but no need to say it again and again .
A. There are ; there is
B. It is ; there is
C. There is ; it is
D. It is ; it is
网友回答
A. There are ; there is
(答案→)B. It is ; there is
C. There is ; it is
D. It is ; it is
解析：第一空it为形式主语，it代指的是真正的主语to say sorry when you knock into someone,形式主语只能选择it，第二空是固定句型，there is no need to do sth 意为，没有必要干某事