Consider the following statements regarding the human brain:
$1.$ The cerebrum has a highly convoluted surface,which provides space for more neurons.
$2.$ The medulla oblongata is connected to the spinal cord.
$3.$ The medulla oblongata contains centers for respiration,cardiovascular reflexes,and gastric secretions.
Which of the above statements are correct?

• A
  All are correct.
• B
  Only $1$ is correct.
• C
  Only $1$ and $3$ are correct.
• D
  Only $2$ is correct.