问题
选择题
—_____ do you send an e-mail to your cousin?
—Sometimes.[ ]
A. How long
B. How much
C. How often
D. How soon
答案
答案：C
搜题请搜索小程序“爱下问搜题”
—_____ do you send an e-mail to your cousin?
—Sometimes.[ ]
A. How long
B. How much
C. How often
D. How soon
答案：C
、过滤、蒸发三个步骤中，玻璃棒所起的作用分别是 ____________ 