According To Chomsky Hierarchy
For CFG L.H.S side should be Single variable,production form is like
S->A where S belongs to Variable and A belongs to Variable and Terminal.(L.H.S sholud be single variable).In Production 4 condition violate.
In Case Of Regular Grammer Same thing follow and some additional also,but L.H.S their should be Single Variable.
In Case Of Context Sensitive
Lets X->Y then
|X|<=|Y|( length of x should be less than or equal to Y).this condition is violate in Production 4 where |Sa|>|b|.
option left only D