Unlike exocrine glands, endocrine glands

a.) release secretions outside the body.
b.) release digestive enzymes.
c.) release secretions directly into the blood.
d.) usually have ducts.

Unlike exocrine glands, endocrine glands release secretions directly into the blood. The correct option among all the options that are given in the question is the third option or option "C". Basically exo means outside and endo means inside. This is the hint that will lead to the correct answer.