Ateratogen: a) may be a virus, a drug, a chemical, radiation, or environmental pollutants is usually inherited from the mother b) cannot cross the placenta during the period of the embryonic stage c) can be counteracted by good nutrition most of the time.

Option-A

Explanation:

A teratogen refers to a agent which can cause abnormal development of the foetus during pregnancy. A teratogen affect the growth of the foetus usually during after 10 to 14 days of conception.

A teratogen is a substance which is usually found in the environment to which the pregnant lady is exposed therefore there are four types of teratogens found: the biological agents which could cause infection, the physical agents like chemicals, metals heat and radiation and the drugs and chemicals from the environment.

Thus, Option-A is the correct answer.

teratogens found in the environment and in extraordinary circumstances can include metals, chemicals, radiation, and even heat. Examples of these teratogens can include mercury, potassium iodide, nuclear fallout radiation, and even high-temperature hot tubs!

eratogens are classified into four types: physical agents, metabolic conditions, infection, and finally, drugs and chemicals.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

straight or amphibians are homeothermic to thermal