It is a teacher’s job to make sure that everyone of his stud

B
这是个主语从句,it是指代to make sure that everyone of his students____confident in preparing himself for the future.这个部分也是从句部分,从句部分又有它自己的主谓宾,everyone of his students是主语,此时考查主谓一致,everyone是代词,单数,故谓语用动单三,feels.
补充：代词each和由every,some,no,any等构成的复合代词作主语,或主语中含有each,every,谓语需用单数.　　Each of us has a tape-recorder.
是啊,没理由选A,而且大家都肯定选B,从语法上也讲不通