要在墙上钉一根水平方向的木条，至少需要______个钉子，用数学知识解释为______．
至少需要2个钉子，解释为经过两点有且只有一条直线．
根据句意及汉语提示，填写单词。
1. I saw Jack sitting (在……旁边) Jim talking.
2. I don't understand the meaning of this (符号).
3. My sister got the answer to the (谜语) very quickly.
4. Many people are against (做实验) on animals.
5. He gave me a (恰当的) example, so I understood it easily.
电流互感器二次保护要绕组合理分配，对确实无法解决的保护动作死区，在满足系统稳定要求的前提下，可采取（）和（）跳闸等后备措施加以解决。
A.近后备起动失灵
B.起动失灵远后备
C.起动失灵远方
D.起动失灵、远后备
