几道初三英语题.(有关定语从句的）

几道初三英语题.(有关定语从句的）
1.It was this reason _______he was late for school.
A.that B.which C.because D.because of
2.There are many boys here,none of_______ like singing.
A.who B.whom C.that D.which
3.Betty said the work would be done by October,_______I doubt.
A.it B.that C.when D.which