23 Paragraph 2 </p> 24 Paragraph 3 8 d: G/ C' ^" o% {% F& `6 {
25 Paragraph 4 & O2 v+ ]4 ^. T% X) l
26 Paragraph 5 ' x( s% P' k& Z& Q
A Study of Sound
# l U; `% s0 m0 _& v- G6 s( E B Highway Police
. ]. h. T9 ]: k' D8 ? C Working Principles
* t% r5 o6 g9 B D Early Use of "Radar" ! v5 E) ^' ?4 D5 C
E Useful Tools % r3 v" t* R. [! L8 z+ \
F Discovery by Chance
( ?( {( m9 M- u4 E6 ? 27 Echo-sounding devices were early used to ( S$ u1 y" B! _' H1 Q: U2 A
28 Ultrasonic device were used to % T6 S8 v% m5 V5 D1 \5 E9 j3 O6 h. p( N2 Y
29 Police use radar on highways to k, L& X% p9 A) f7 N
30 Radar helps pilots to 1 t& T2 I5 U& d- |) H" P
A detect nearby objects : d3 K, {/ t7 r" t: f3 J5 {
B determine the depth of the ocean water 8 ?% w1 d+ h: G* N6 h3 c) x" P
C decide how fast you drive www.examw.com
7 z, D+ M: K9 T; w+ U0 G D stop passing ships
4 h( v7 I( F7 `* ?3 E E map the ocean floor
! E3 O# w2 f8 L) f% g F observe water flow
: i+ Y' J( J* Q8 T 【参考答案】
# S/ T9 V, p( T& f 23. D 24. F 25. C 26. B 27. E 28. B 29. C 30. A |