关于happen,take place,come about用法区别以及total
有这样一道题目They used to be good friends but now they are like strangers.How( )this( A.did;come about B.did;happen to C.was;ended up D.was;happened 应该选择A,可是不知道为什么.所以想问一下这几个词语的用法区别在哪里.
( ),there must have been 20000 people there,that is,there are( )20000 people there.A.On total;a total of B.In total;a total of C.In total;the total of D.On total;the total of 为什么选择B,请麻烦解释一下这几个词的用法.on total/in total a total of/the total of