$\begin{array}{1 1} \text{a. Endocrine glands regulate neural activity, but not vice versa.} \\ \text{b. Neurons regulate endocrine activity, but not vice versa.} \\ \text{c. Endocrine glands regulate neural activity and nervous system regulates endocrine glands.} \\ \text{d. Neither hormones control neural activity nor nrurons control endocrine glands.} \end{array}$
