-- _______ do you exercise? --Three times a week. A. When B. How often C. How long D. How much
“不敢高声语，恐惊天上人”。这里的“高”指的是声音的_______ (填“音调”、“响度”或“音色”)大。月宫里的嫦娥不会听到你说话的声音，因为____
下列离子方程式书写正确的是（ ） A．铜溶于浓硝酸： Cu +4HNO3 (浓) = Cu2++ 2NO2↑＋2H2OB．
关于下列三种粒子的说法正确的是 A．表示同一种原子 B．X表示阳离子 C．Y显电中性 D．Z表示阴离子
During the period of recent terrorist activities, people ____ not to touch any unattended bag. A. had always been warned B. were always being warned C. are always warning D. always warned
I would love _______ to the party last night but I had to work extra hours to finish a report. A. to go B. to have gone C. going D. having gone
思乡是文学作品中常见的主题之一，请写出古诗中表达这种情感的连续两句 ， 。
．（3分）如图所示电路中，电源电压为6V，当开关S闭合后，电流表A1的示数为0.2A，电流表A2的示数为0.6A。求：电阻R1、R2 的阻值各为多少?
的值是 （ ）
B 
C 
D 
