题目

How hard we have all prayed(祈祷) to grow up quickly, and looked forward to the happy days of being a grown-up and enjoying the many interests that a youth should have. At last, you have grown up. At least you are no longer a child. They call you “young lady”. You then enjoy the pleasure of being a young lady. You are proud of being a grown-up teenager. People welcome you-this young lady-heartily. You are glad that your prayer has been answered. But there is always something that troubles you a lot. You say; “Papa and Mama, give me some money please. My pocket money is all gon（09年广州市调研）如图示电路中，电源电动势E= 9V、内阻r= 3Ω，R =15Ω。下列说法中正确的是   A.当S断开时，UAC=9VB.当S闭合时，UAC=9VC.当S闭合时，UAB=7.5V，UBC=0D.当S断开时，UAB=0，UBC= 0