A relation from P to Q is

• A

  A universal set of $\mathrm{P}\times \mathrm{Q}$

• B

  $\mathrm{P}\times \mathrm{Q}$

• C

  An equivalent set of $\mathrm{P}\times \mathrm{Q}$

• D

  a subset of $\mathrm{P}\times \mathrm{Q}$