$X -$ It is very important for the process of evolution.
$Y -$ Crossing over is the exchange of genetic material between two homologous chromosomes.

• A
  Both are true for mitosis.
• B
  Both are true for meiosis.
• C
  $X$ is true for mitosis,$Y$ is true for meiosis.
• D
  $X$ is true for meiosis,$Y$ is true for mitosis.