Question

what happens when the bladder becomes full?
the bladder sends signals to the brain instead of the spinal cord.
the bladder starts filtering urine.
the bladder becomes smaller in size.
the bladder stops producing urine.
the stretch receptors in the bladder wall send signals to the spinal cord.

Explanation:

When the bladder is full, stretch receptors in its wall detect the stretch. These receptors send signals to the spinal cord (not the brain as the first option wrongly states). The bladder does not filter urine (that's the kidney's job), it doesn't become smaller when full (it expands to hold urine), and it doesn't produce urine (urine is produced by the kidneys).

Answer:

The stretch receptors in the bladder wall send signals to the spinal cord.