Consider the following information about elements $P$ and $Q$:

Element	Period and Group
$Q$	Period $2$,Group $15$
$P$	Period $3$,Group $2$

Then the formula of the compound formed by $P$ and $Q$ elements is:

• A
  $PQ$
• B
  $P_3Q_2$
• C
  $P_2Q_3$
• D
  $PQ_2$