II. 单项选择（共15小题，每小题1分，满分15分）
从每小题A、B、C三个选项中,选出可以填入空白处的最佳选项,并将其字母标号填入題前的括号内：
( )21. —Do you know Wang Yaping, the woman astronaut in Shenzhou-X?
—Yes, _________physics teaching in space was amazing.
A. she B. her C. hers
( )22. Shopping on line is a big _______ for the traditional shops.
A. challenge B. solution C. decision
