56._________A.if B.whetherC.either D.neither

A: The students work hard. B:_____A．So do they.B．So they do.C．So we do.D．Neither do they.

_________[A] if [B] unless [C] as [D] lest

_________(58)A.if B.whetherC.no matter D.only

Some scientists doubted________.A.if the Gardener

_________(64)A.if B.how C.when D.why

60._________A.and B.or C.nor D.neither