—Where have you _________ all day?

—I came back at noon and I _________ in this room ever since.

A．gone; had been

B．gone; was

C．been; have been

D．been; am

各类杆塔的正常运行情况，应计算下列哪些荷载组合？（）

A.基本风速，无冰，未断线（包括最小垂直荷载和最大水平荷载组合）

B.设计覆冰，相应风速及气温，未断线

C.电线不均匀覆冰，相应风速，未断线

D.最低气温，无风，无冰，未断线