-- Why didn’t you come to see the film with your parents last weekend?

-- I _____ my lessons for the month- exam.

A．was preparing

B．prepare

C．prepared

D．have prepared

计算题：一条10kV配电线路的TV二次电压U为100V，TA二次电流I为3A，功率因数cosψ=0.8，三相电压对称，三相负载平衡，其中TV变化为l0kV/100V，TA变化比为300A/5A，试计算其折算到一次侧的功率。