问题
选择题
已知⊙O1和⊙O2相切，两圆的圆心距为10cm，⊙O1的半径为4cm，则⊙O2的半径为（ * ）.
A．3cm
B．6或14cm
C．2cm
D．4cm
答案
答案：B
当⊙O1和⊙O2内切时，⊙O2的半径为10+4=14cm；
当⊙O1和⊙O2外切时，⊙O2的半径为10-4=6cm；
故⊙O2的半径为6或14cm．
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已知⊙O1和⊙O2相切，两圆的圆心距为10cm，⊙O1的半径为4cm，则⊙O2的半径为（ * ）.
A．3cm
B．6或14cm
C．2cm
D．4cm
答案：B
当⊙O1和⊙O2内切时，⊙O2的半径为10+4=14cm；
当⊙O1和⊙O2外切时，⊙O2的半径为10-4=6cm；
故⊙O2的半径为6或14cm．
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| I had a cigarette one morning as I walked along the wooded path toward my house deep in the forest. I know smoking is bad for me, and 1 . I had tried to kick the habit, but 2 . Not even when my aunt Bernie got lung cancer. How many times had she begged me to give _3_ up? After she died, I made up my mind to stop, and did so, but 4 I started up again. The house had been one of Aunt Bernie's favorite places to stay. Lately, I had earned some 5 income by renting it out. New renters were 6 to arrive that afternoon. The house has no electricity, so I had to 7 there was enough propane (丙烷) in the tank to 8 the fridge and the stove (火炉). Seeing the house in the distance through the trees, I thought about 9 . I could still hear her 10 telling me, "Give up smoking; it will 11 you." As I was 12 the house, the voice grew stronger, 13 my aunt were standing right beside me. Finally, I couldn't 14 it any longer. I smothered (弄熄) it. "Fine, Auntie, I 15 . See?" I continued down the path, 16 the urge to light up again. Reaching the house, I opened the door. Whoa! I stepped back. The 17 was strong. Propane gases! I ran around to the back and found the problem. The previous 18 had forgotten to turn off the propane tank before they left. The house had been 19 up with gas for a week! If I had still been smoking that cigarette... I thought now, 20 . My aunt Bernie was right. Smoking can kill me. The next day I started a quitsmoking program, and I haven't lit up since. | ||||
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