Correct Answer: (2) Some specialized cells mark and other cells engulf microbes during immune reactions.

An antigen is a foreign macromolecule that does not belong to the host organism and that elicits an immune response. When an antigen is recognized by the immune system, it is marked as "harmful" and thus engulfed by the sleukocytes.

Incorrect Answers:

Antibiotics have various mechanisms of action depending on the organism/ingredient used. Most antibiotics (e.g., Penicillins, Glycopeptides) block the cell wall formation of the pathogenic bacteria.

It is true that embryonic development occurs during pregnancy, however, this is not the explanation for the illustration showed. Embryonic development is characterized by simultaneous cell divisions and differentiation.

Cloning is the process of copying the exact genetic information of an organism, thus, all cells will differentiate in the same manner, whether normal or abnormal.