—What time is he going to start?  

—_____. [ ]

A. It's half past four now

B. At half past four

C. about four hours

D. This morning

系统如题53图所示，系统中各元件在统一基准功率下的标幺值电抗为G1：=0.1，=0.2，T1：YNO，d11，，中性点接地电抗；T2：Y0/Y0/△，x1=0.1，x2=0，x3=0.2，，T3：Y/△-11，，L1：，，电动机M：。当图示f点发生A相接地短路时，短路电流标幺值为（）。

A.6.696

B.8.636

C.7.396

D.8.969