Wemust______thattheexperimentiscontrolledasrigidlyaspossible.
Whenhesuddenly________upthesubjectofgeneticengineering,therewasanembarrassedsilence.
It'smore________tobuyaseasonticketifyoutraveleveryday.
WhenIcamethroughthecustomsattheairport,Ihadtopay________onaclockIhadbought.
ShegotajobasanassistantstagemanagerattheCambridgeArtsFestivalTheatre,thinkingthatitmight________toacareerasaplaywright(剧作家).