In China ___ graduates go abroad to have a further study eve

因为A修饰不可数名词
B many a 后面加可数名词单数,表示许多.
“many a＋单数可数名词”形式上为单数,但意义上为复数(意为“许多”),若用作主语,其谓语通常与形式一致而不与意义一致(即谓语用单数).如：
Many a student has seen the film.许多学生看过这部电影.
Many a fine man has died in that battle.许多优秀的士兵死于那次战役.
Many a ship has been wrecked on those rocks.许多船只毁于那些礁石之上.
Many a young man has tried and failed.很多年轻人都试过,而且失败了.
Many a successful store has paid its rent cheerfully.许多成功的店铺都非常乐意地付了房租.
注：“many a＋单数名词”是一个十分正式的结构,在口语或非正式文体中一般都用 many＋复数名词”代之.
D同A,后面加不可数,其用法为:a large（great,good）amount of ＋不可数名词,谓语动词一般用单数；但（huge,great,good）amounts of ＋不可数名词,作主语时,谓语动词要用复数.
A large amount of damage has beend one by the earth quake．
Large amounts of money were spent on the bridge．
综上,C入选

A /D 专指不能量化来数的名字，比如时间，影响，麻烦什么的
B 意思是多数的什么什么啊，大部分的意思，这个是概率的问题

A 只能接不可数
B 后面只能接单数
D 理由同A