The client with cirrhosis is put on a sodium-restricted diet and a diuretic. The nurse would expect to administer a potassium-sparing diuretic. Which of the follow is a potassium-sparing diuretic

A. Furosemide (Lasix).
B. Spironolactone (Aldactone).
C. Hydrochlorothiazide (HydroDIURIL).
D. Ethacrynic acid (Edecrin).

（1）若金属线圈的电阻为R，求金属线圈的ab边刚进入区域1 的瞬间，线圈克服安培力做功的功率为多少？

（2）若金属线圈的质量为m ，求金属线圈通过区城l 的过程中，线圈中产生了多少热量?

（3）若金属线圈的质量和电阻均为未知，求线圈通过第二个磁场区域后（cd 边离开磁场）的速度。