Let G be a group of order 20 in which the conjugacy classes have sizes 1, 4, 5, 5, 5. Then which of the followings is/are TRUE ?
(A)    G contains a normal subgroup of order 5.
(B)    G contains a non-normal subgroup of order 5.
(C)    G contains a subgroup of order 10.
(D)    G contains a normal subgroup of order 4.