The figure below shows a three-dimensional view of an anther. Identify $P$ and $Q$.
$\quad\quad\quad\quad \quad P \quad\quad\quad\quad Q$

• A
  Pollen grains $\quad$ Pollen sacs
• B
  Pollen mother cells $\quad$ Pollen sacs
• C
  Pollen grains $\quad$ Microsporangium
• D
  Pollen mother cell $\quad$ Microsporangium