设有下 * * 条路由：172.30.129.0/24、172.30.130.0/24和172.30.132.0/24。如果进行路由汇聚，能覆盖这3条路由的地址是 (29) 。
A．172.30.128.0/21
B．172.30.128.0/22
C．172.30.130.0/22
D．172.30.132.0/23
参考答案：A
解析：[要点解析] 解答这类试题的基本思路见表1-3。
[*]
由表1-3的求解结果可知，能覆盖172.30.129.0/24、172.30.130.0/24和172.30.132.0/24这3条路由的地址是172.30.128.0/21。
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| I believe in miracles (奇迹) because I've seen so many of them. One day, a patient was referred to me who was one hundred and two years old. " There's a 1 in my upper jaw," she said. "I told my own dentist it' s nothing, but he 2 I come to see you." Her eighty-year-old son accompanied her. He would 3 to add something,but she stopped him. She wanted to tell everything herself. I found a large cancer that spread over most of the 4 of her mouth. A careful examination later 5 that it was a particularly bad sort of cancer. During her next appointment, I explained to her the 6 of the problem. She clasped my hand in hers and said," I know you're worried about me, but I'm just 7 " I thought otherwise. After considerable 8 on my part, and kindness on her part because she wanted to 9 me, she agreed to have me refer her to a cancer surgeon. She saw him, but as I expected, 10 treatment. About six months later she returned to my office, still energetic and 11 . " How are you?" I asked. " I'm just fine, honey," she responded 12 high spirits."When can I get started on fixing my dentures (假牙)?" Surprised to see her at all, I answered 13 ," Let me take a look in your mouth and we'll see about it." " I couldn't believe my eyes. The cancer that had 14 nearly the entire roof of her mouth was gone-only one small area of redness 15 . I had read of such things happening,but had 16 seen them with my own eyes. That was my first miracle. Since then I've seen many others, because they keep getting 17 to see. In fact, miracles are daily events for me now. And people are all miracles, 18 through them we have a chance to know ourselves and to 19 the miracles of one another. Since my first miracle, I've come to understand that the time and place for a miracle is 20 we choose to find it. | ||||
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