如图所示电路中，R₁=R₃＜R₂=R₄，在ab两端接上电源后，设每个电阻所消耗的电功率分别为P₁、P₂、P₃、P₄，则它们的大小关系是（　　）

A．P₁=P₃=P₂=P₄

B．P₂＞P₁＞P₃＞P₄

C．P₂＞P₁＞P₄＞P₃

D．P₁＞P₂＞P₃＞P₄

句型转换。

1. Li Ming has already finished his homework.（改为一般疑问句）

   _____________ Li Ming _____________ finished his homework yet?

2. Both of the boys are good at basketball.（改为否定句）

   ______________ of the boys _____________ good at basketball.

3. Laura has never been to Hong Kong.（改为反意疑问句）

   Laura has never been to Hong Kong, ____________ ___________?

4. Mr. Brown has taught in the school since 1990.（对划线部分提问）

   _____________ _____________ has Mr. Brown taught in the school?

5. The twins came to China three years ago.（改为现在完成时态的句子）

   The twins have _____________ _____________ China for three years.