An advertising campaign urges pregnant women to get good prenatal care by saying that all of the structures that we recognize as human (including arms, legs, eyes, internal organs, and a beating heart) have already developed early in pregnancy. Having studied prenatal development, you know that the most accurate statement is that these structures are present, at least in rudimentary form, by:

The end of the second month of pregnancy.

Explanation:

By the end of the second month of pregnancy, all the organs, systems, and structures in the embryo are rudimentary formed, and in their place. Some of the organs work, like the heart, and others don't, like the eyes, which are still closed. As regards, their legs and arms, the embryo will have arms and legs buds that will be limbs some weeks later.