During the prenatal period of development, x-rays, infections, tobacco, alcohol, and toxic substances are examples of the critical period exemplars discriminative stimuli teratogens

Teratogens

Explanation:

Teratogens are substances or or other factors that can cause congenital abnormalities. This disability is also known as birth defects.

These abnormality arise in the third week to eight week of pregnancy whwn the major organ system are forming in fetus.

Some examples of teratogens are certain chemicals, medications, tobacco, alcohol, x-rays.

answer; the correct answer is (beta)

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.