71.
Pick up the correct statement from the following:

72.
Pick up the correct statement from the following:

73.
Pick up the correct statement from the following:

74.
Pick up the correct statement from the following:

78.
Critical angle of electromagnetic radiation takes place if

79.
The reflection of solar energy is characterized by the water content in the leaf, in the reflective optical infrared:

80.
Which one the following is a correct statement?