She ____________ the piano every day. [ ]
A. playing
B. plays
C. play
D. played
答案:B
生铁和足量的稀硫酸反应后,往往有少量不溶物出现,该不溶物是( )
A.Fe
B.C
C.FeSO4
D.Fe2(SO4)3
景观空间异质性通常可以分为()和功能异质性两大类型。