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【单选题】
Which statement was NOT mentioned about viewing an eclipse?A.
Sunglasses block out only a limited amount of the sun's ultraviolet rays that can damage the eye.
B.
Sunglasses can only filter harmful rays during total solar eclipses at their greatest magnitude.
C.
Sunglasses tend to cause the center of the eye to enlarge allowing in more intense light.
D.
Sunglasses should be used when any part of the sun is visible.
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【简答题】在图所示的轮系中，已知各轮齿数Z 1 =20，Z 2 =40，z 3 =20，z 4 =30，z 5 =80，求传动比i 1H 。
【简答题】在图示轮系中,已知z1=25、z2=50、z2'=20、z3=30、z4=40、 z4'=30、 z5=45、 z5'=20、z6=80。 (1)若已知1轮转向n1如图所示,请在图上标出其余各轮转向; (2)求传动比i16。 (3)请指出图示轮系中的惰轮,并说明它的作用。 齿轮系1.docx