几道关于名词性从句的问题

1.The seaside here draws a lot of tourist every summer,Warm sunshine and soft sands make______it is. A.what B.which C.how D.where 2.You can only be sure of ______you have at present; you cannot be sure of something_____you might get in the future. A.that;what B.what;/ C.which;that D./;that 3.Why not try your luck downtown，Bob?That's_______the best jobs are. A.where B.what C.when D.why 4.Having checked the doors were closed, and_______ all he lights were off, the boy opened the door to his bedroom. A.why B.that C.when D.where