Vaccines can protect against viruses by triggering the production of

The correct answer is - antibodies.

Explanation:

Vaccines are the biological substance or the preparation that helps in building the active acquired immunity from a particular disease. Vaccines are basically weakened or dead infectious agents or particles that induce or active the B cells to produce antibodies and memory cells.

These antibodies are formed by the vaccines by triggering the production of B cells. This process of injecting vaccines is known as vaccination.

Thus, the correct answer is - antibodies.

stress fractures occur largely in the feet and legs and are common in sports that require repetitive impact, primarily running/jumping sports such as gymnastics or track and field.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.