The following diagram shows the internal structure of a root hair. Identify the parts labelled as $X$ and $Y$.

• A
  $X$-Nucleus, $Y$-Root epithelial cell
• B
  $X$-Cytoplasm, $Y$-Root epithelial cell
• C
  $X$-Nucleus, $Y$-Cell wall
• D
  $X$-Root epithelial cell, $Y$-Nucleus