-----I wonder if you could go with me to the supermarket.

------- Don’t disturb me. I _____________my experiment report all the morning and haven’t finished yet.

A．write

B．was writing

C．have written

D．have been writting

可控整流有源逆变电路通常应用于（）场合。

A、直流可逆电力拖动

B、高压直流输电

C、家用电器

D、UPS电源