比赛中,第一裁判员鸣哨后,发球队员必须在5秒内将球发出。
参考答案:错
_______ my sister three times today but her line was always busy.
A.I’d phoned
B.I’ve been phoning
C.I’ve phoned
D.I was phoning
滴有石蕊试液的稀硫酸分别与下列物质混合后,溶液一定呈红色的是( )
A.Na2O
B.BaCl2
C.KOH
D.NaNO3