The right answer is Stimulants speed up the central nervous system
A stimulant is a substance that increases the activity of the sympathetic nervous system facilitating or improving certain functions of the body. Common stimulants include caffeine in tea and coffee, and nicotine in large amounts in tobacco.
Stimulating substances increase the activity of the sympathetic system quite gradually but in a prolonged manner, being distinguished from those having a rather fast but relatively limited exciting effect.