7、own17.I______backpainforyears.A. have sufferedfrom B. havesuffered C. hadsufferedfrom D. hadsuffered18.Therehasbeen______accidentsonthehighwaybecauseoftheheavyfog.A.akindofB.aseriesofC.apairofD.apieceof19.—Let'sgoswimming,shallwe?—_______.(上海春季)A.It'smypleasureB.Itdoesn'tmatter