Which neurotransmitter regulates sleep, mood, attention, and learning, and too little of this neurotransmitter can cause depressed mood?

Serotonin and Dopamine

Dopamine is a neurotransmitter which is usually associated with attention and learning, and too of it little can be related to several forms of depression.  

Also, Serotonin plays a part in the development of mood, appetite and is associated with sleep, whereas; too little of serotonin is related to depression.

b) trade is easy because of the direct line between their major ports. bilateral trade reached 89,6 thousand million.

what are the answer choices?