题干
______ when the visitor comes in.
A： Raise to your feet
B：Rise to your feet
C：Rising to your feet
D：Raising your feet
答案(点此获取答案解析）
B
______ when the visitor comes in.
A： Raise to your feet
B：Rise to your feet
C：Rising to your feet
D：Raising your feet
点，针对这一特点，下列哪项不是防护生物武器的有效措施? （ ）
