Consider the folllowing grammar
$ S\rightarrow AaS \ |\ b$
$ A\rightarrow c \ |\ d \ |B$
$ B\rightarrow AgC \ |\ AhC \ | \ DgC | \ DhC$
$C\rightarrow c \ |\ d \ | \ D$
$ D\rightarrow eBf$
Which of the following are viable prefix ?
$ \left ( 1 \right )Aab$
$ \left ( 2 \right )ca$
$ \left ( 3 \right )cab$
$\left ( 4 \right )AgCS$