Answer
a) Nervous system.
d) endocrine system.
Work Step by Step
Homeostasis is the optimal function of the body altered according to the external stimulus.
Now with this question it is a matter of eliminating the systems that are not involved in maintaining homeostasis, these are the digestive, reproductive, and cardiovascular which are each responsible for the breakdown of food to get nutrients and excrete waste, reproductive is for the production of zygotes and children, while cardiovascular is responsible for the transportation of nutrients throughout the body.
The endocrine system is the chemical system designed to maintain long term homeostasis through the use of hormones to control, growth and metabolism. The nervous system on the other hand is based on a system of chemical/electrical currents to create action potentials to stimulate the brain. It is a very fast system handling the day to day needs of the body.
