$A$ is an aqueous acid; $B$ is an aqueous base. They are diluted separately,then:

• A
  $pH$ of $A$ increases and $pH$ of $B$ decreases
• B
  $pH$ of $A$ increases and $pH$ of $B$ decreases till $pH$ in each case is $7$
• C
  $pH$ of $A$ and $B$ increase
• D
  $pH$ of $B$ and $A$ decrease