23 Paragraph 2 </p> 24 Paragraph 3 2 \* `% F* S* }
25 Paragraph 4 # R) d3 u! ?: S" s4 D3 E% u
26 Paragraph 5 % n& T2 ], B; G2 A" d2 A
A Study of Sound
; l: \$ ~' H9 n( Z ? B Highway Police ! p0 C; }6 X W, n, N9 k. J" {- m
C Working Principles ) d- R- X1 z$ V2 R
D Early Use of "Radar" {* @8 e# v/ _
E Useful Tools / M4 D, n7 P: z6 z7 ?0 x% w$ n* t
F Discovery by Chance $ m) B! u2 G6 |- R6 ~
27 Echo-sounding devices were early used to
5 x& n0 m$ F, R3 s' z- x 28 Ultrasonic device were used to / m9 S( s% f. x* h4 l( Q
29 Police use radar on highways to
; {/ e1 i5 v% `8 d 30 Radar helps pilots to
( m9 Q5 Z1 J$ c1 B A detect nearby objects
4 t- l) j! s( N B determine the depth of the ocean water
% j) y/ M+ Z; T4 u C decide how fast you drive www.examw.com; k" E- a: t R- Y4 a1 _4 p' x$ x) v
D stop passing ships ' K, g0 z; r2 i; O3 a+ g4 y" p
E map the ocean floor , ^+ U) u$ w2 m k
F observe water flow * ]( f" e5 ]- B x9 F$ r) B2 N
【参考答案】 : s* z w0 c. [& t5 i) I
23. D 24. F 25. C 26. B 27. E 28. B 29. C 30. A |