Manypeopleattendvariouspubliclectures,chiefly______themselvesfamiliarwiththelatestdevelopmentofdifferentfields.

Nomatterhowfrequently_____theworksofBeethovenalwaysattractalargenumberofpeople.

Everyonehopesthatwecandosomethingtomakethingsbetter,sowecan'thelp______underthestress.

设随机变量X，若D(X)=3，则D(一X+3)=()．

_____theirrealeconomicsituations,theygotsomerelieffundfromthegovernment.