Theproblem________whenthestudentsrefusedtodotheirhomework.
A、aroseWhenhesuddenly________upthesubjectofgeneticengineering,therewasanembarrassedsilence.
A、took________somanypeopleintheUnitedStatesbeenoutofworkastoday.
A、MorethaneverbeforeIt________asashocktorealizethatIwasnotaloneintheroom.
A、cameSinceWilliamhadbeenseriouslyillforseveralmonths,hisparentswereworriedabout________toreturntoschoolfull-time.
A、hewanted