Sleep often improves memory. How? A. Synapses increase their supply of serotonin and norepinephrine. B. Certain synapses become weakened, enabling others to stand out by contrast. C. Overall brain...

Sleep often improves memory. How?
A. Synapses increase their supply of serotonin and norepinephrine.
B. Certain synapses become weakened, enabling others to stand out by contrast.
C. Overall brain activity increases.
D. The brain increases its ratio of sodium ions to potassium ions.