$Statement\; 1$: Zygote is a single cell.
$Statement\; 2$: Two haploid cells fuse to form two diploid cells.

• A
  $Statement\; 1$ is True,$Statement\; 2$ is True; $Statement\; 2$ is the correct explanation for $Statement\; 1$.
• B
  $Statement\; 1$ is True,$Statement\; 2$ is True; $Statement\; 2$ is not the correct explanation for $Statement\; 1$.
• C
  $Statement\; 1$ is True,$Statement\; 2$ is False.
• D
  $Statement\; 1$ is False,$Statement\; 2$ is True.