Historically, global climate
a. has always been the same.
c. has varied greatly over time.
b. has varied slightly over time.
d. none of the above.

Option B, has varied greatly over time

Explanation:

The climate change on planet earth is a long and continuous process which is ongoing till today. It is believed that some four billion years ago, the atmosphere of earth was made up of radical ions and also the earth was excessively hot. After this phase the life evolved on earth and the climate also improved. After several years of its formation, the earths climate again took a drastic turn when the ice age came and every thing just got frozen. This occurred during the Pleistocene Epoch period some 2.6 million years ago.

Later on , the ice age also passed and now a days temperature is rising year by year due to global warming.

Due to these drastic conditions it can be said that the climate of earth changed greatly over time.

there are mainly three domains in biological classification namely; archaea, bacteria, and eukarya.

archaea includes all the prokaryotic cells which are characterized by their lipid membranes. they have branched hydrocarbon which is attached to glycerol through an ether linkage.

bacteria includes all the prokaryotic cells, the cell membrane of which are made up of the unbranched fatty acid chain. in addition, they are attached to glycerol through an ester bond.

eukarya includes all the eukaryotic cells, that is, the cells contain a nucleus and other membrane-bound cell organelles.

they can be autotrophic as well as heterotrophic, unicellular as well as multicellular

they include kingdoms like protista, plantae, animalia, fungi et cetera.

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explanation:

scientists have discovered that hiv does not cause aids by the virus's direct effect on the host's immune cells, but rather through the cells' lethal influence on one another. researchers from the gladstone institutes have revealed that hiv does not cause aids by the virus's