人耳能区分两个相连声音的时间间隔至少为0.1s,一个人站在高墙前至少多少米才能听到自己击掌的回声?
17m
— Sit down,please.
— ________. [ ]
A. Yes
B. No
C. Fine
D. Thank you
—Is that your pencil?
—Yes, it is. It's ______ pencil. [ ]
A. his
B. her
C. my
D. your