Teratogens: select one: a. are environmental agents that can harm the embryo or fetus. b. are most damaging during the fetal period of development. c. are only those substances the mother's body produces. d. harm the fetus only when taken in extremely large doses.

The answer is A. Teratogens are substances that impair the proper development of embryo or fetus. They include drugs, infections, radiation, and chemicals. The agents could cause the fetus to be physically or mentally impaired. Children born having been exposed to teratogens that affect their brain development could exhibit reduced IQ, communication challenges, and etcetera.

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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