图所示电路中电流源发出功率为        。

单项选择题A． B． C． D．

问答题Directions:Complete the following paragraph by choosing one statement from the column below. (1)_____________________________________________. Where Britons end certain words with -se Americans usually end the same words with -ce (British practise vs. American practice); (2)________________________ (British defence vs. American defense). Notice also the British preference for final -re over the American -er (metre vs. meter). Finally most Americans consider neighbor a correct spelling, (3)________________________ and spells it in another way. A. but a Briton characteristically adds a u B. but American spelling prevails among the youth C. Minor differences exist between American and British spelling D. the reverse is sometimes true, too 请将答案序号按照题号顺序写在下面横线上。答案之间用空格隔开。 _______________________