—The project has been held up by a sudde
题型：选择题
问题：
—The project has been held up by a sudden change in temperature for a week.
—I'm afraid the terrible weather will________for some time.[ ]
A. keep back
B. keep up
C. keep out
D. keep on
题型：选择题
下图所示装置中，X是铁，Y是石墨电极，a是硫酸钠溶液，实验开始前，在U 形管的两边同时各滴入几滴酚酞试液，下列叙述正确的是
A．合上K1，断开K2，X极放出H2
B．合上K1，断开K2，Y极为阳极
C．合上K2，断开K1，Y极的电极反应式为：O2+2H2O+4e-=4OH-
D．合上K2，断开K1，电解一段时间，X电极附近溶液呈红色