A：防止声响从口腔进入，听不清楚
B：防止鼓膜内外音响度不同，听不准确
C：防止鼓膜内外气压不平衡，损伤鼓膜
D：防止脑震荡
32____28 69____71 58____85
反应时间/min
n（SO2）/mol
n（O2）/mol
0
0.10
0.060
t1
0.012
t2
0.016
选词填空。
A. This is Mary. She's nine. She's tall. She's thin.
B. This is Danny. He's six. He's short. He's fat.
C. This is Eddie. He's nine. He's short. He's thin.
____（.）
