七年级英语完形填空
ThefamiliesinBritainaresmall.Itisunusualforparentstohavemorethantwochilren.Whenchildrenareabouteighteenornineteen,theyleavetheirparents'home,andtheyoftengotoadifferentcity.S_____theyonlyvisittheirparentstwoorthreetimesayear.我填的是so,但正确答案是sometimes,哪个更好?