A
B
C
D
8
A B C D
9
A
B
C
D
10 202000H 20000Hz
A
B
C
D
11 500mL _____kg/m 3
_____kg _____
0.9 103kg/m3
12 _____
_____ _____
13
_____ _____
14
152017 531 2s
_____ _____
16 1m/s 6m _____s
_____( )
17 1.0 103kg/m 3
0.9 103kg/m3
200g
450mL
2018.9