Question 1
Choose the most suitable definition of a stimulus.
The right answer is the one marked above.
A change arising in the external or internal environment that is capable of producing a response. The clause "capable of producing a response" is essential.
“A change arising in the external or internal environment” is close but incomplete — not every change is a stimulus; it needs enough strength to produce a response. Linking organs together while responding is the definition of co-ordination.