The term 'flora' in the context of natural vegetation refers to
Options: assemblage of plant species living in association with each other in a given environmental frame, plants of a particular region or period, listed by species and considered as a group, a large tract covered by trees and shrubs and its administration for assessing economic benefits, role played by species of animals in the maintenance of ecological balance
Benjamin Franklin was a prolific inventor. He invented the lightning rod, the Franklin stove, studied electricity, discovered the Gulf Stream, started the first library, and on and on. Among his many other inventions, what musical instrument did he invent?
Options: the intensity of light emitted by them changes with time, the distance of the stars from the earth changes with time, the refractive index of the different layers of the earth's atmosphere changes continuously, consequently the position of the image of a start changes with time, the light from the star is scattered by the dust particles and air molecules in the earth's atmosphere