71 What are hormones?

Secretions of ductless glands

72 The velocity of radio waves is same as that of

Elastic waves

73 In Rutherford atomic model, the path of electrons will be

Circular

74 The Salvia in the mouth acts upon

Starch

75 Gene is

An elementary unit of heredity

76 A blood vessel that carry deoxygenated blood is the

Pulmonary artery

77 The best source of vitamins for a high school pupil is

A properly varied diet

78 The science for the study of old age is known as

Gerontology

79 The instrument used to detect the radiation just outside the red end of the visible spectrum is

Thermopile

80 The most destructive enemy of forests is

Fire