He stood at the gate, __________for his mother. A. waited B. waiting C. waits D. and waiting
已知向量a=(-3，4)，向量b∥a，且|b|=1，那么b= .
—Can you your absence last Friday? —Well, my car broke down and I had 10 get it taken to a garage． A. settle down B．depend on C．account for D．refer to
选修4－2：矩阵与变换(本题满分10分) 已知矩阵，若矩阵属于特征值3的一个特征向量为，属于特征值－1的一个特征向量为，求矩阵．
下列化学用语表示正确的是 A．KClO3：表示氯酸钾 B．K2MnO4：表示高锰酸钾中钾元素的化合价为+1价 C．2Fe2+：2个铁离子 D．2N2：表示两个氮原子
用恰当的化学用语回答下列问题： ⑴两个氢分子________ ；（2）n个硫酸根离子_______；（3）五氧化二氮中氮元素 显 +5 价___________；（4）最简
Women of the Night? I spent thirty-nine years of my life as an_____41_____(educate). As a school administrator, I was ever fortunate to hire a retired headmaster from Fulton County. She was a deli
—What shall I do with this passage? —Just _____the main idea of it . A．finding out B．found out C．find out D．to find out
是角
终边上一点，且
，则
的值为（ ）
C．4 D．
