71 As a balloon is filled with Carbon Dioxide, the buoyant force of the air outside the balloon

Increases

72 Roentgen rays are

Sun rays

73 Light is

A form of energy

74 An object that reflect light of all wavelengths appears

White

75 An object that absorb light if all wavelengths appears

Black

76 Comparing to air, sound waves in water travels

Much faster

77 What is an echo?

A sound repeated by reflection

78 The scientist that did some experiments with gravity first of all was

Galileo

79 Scientifically speaking, all motions are

Relative

80 A Mercury is a

Metal but is present in liquid form at room temperature