Which option expresses the main idea of the chapter most correctly?

Correct answer: Organisms detect stimuli and give coordinated responses through nervous, hormonal, or chemical control

The central idea of Control and Coordination is that organisms detect internal or external stimuli and organise suitable responses. Animals mainly use receptors, the nervous system, and hormones, whereas plants rely largely on chemical messengers and changes in growth or cell turgor. Thus option A includes the major mechanisms and applies to living organisms broadly. The other choices restrict coordination to nutrition, bones, or only one group of organisms, so they are incorrect.