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Subject :NSO    Class : Class 3

When astronauts are out in the space, either they communicate using radios or talk to one another by touching their helmets. Which of the following statements holds true about communication in space?
1.Sound is a vibration that cannot travel through vacuum.
2.Sound vibrations can travel through the material of the helmet to the other.
3.Radiowaves can travel through vacuum.
4.Helmets have speakers built in them which produce sounds when touched.

A4 only
B2 and 3
C1, 2 and 3
D1 and 4

Ans 1:

Class : Class 5

Ans 2:

Class : Class 4
i am confused

Ans 3:

Class : Class 1

Ans 4:

Class : Class 3

Ans 5:

Class : Class 5
ANS A is correct

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