What does the endocrine system do?

The endocrine system is responsible for secreting hormones into the bloodstream. Option A is incorrect because it is the nervous system that controls muscle movement. Option C connects to the nervous system, not the endocrine system. Option D refers to the sensory system, which is also not part of the endocrine system. Therefore, the correct answer is B as it accurately describes the primary function of the endocrine system.