___ into use in April 2000, the hotline was meant for residents   reporting water and heating supply

breakdowns.   [ ]

A. Put        

B. Putting    

C. Having put    

D. Being put

室性期前收缩的心电图特点是（）

A.代偿间歇不完全

B.可见逆行性P′波

C.T波方向与QRS主波方向相反，其前可见P′波

D.完全性代偿间歇

E.QRS波群时间≥0.12s