Answer : 7
According to Lagrange's theorem, for any finite group G, the order (number of elements) of every subgroup H of G divides the order of G.
Note : Order = numberof elements in group
So subgroup size must be from this : 1, 5, 7, 35 (since all are divides the order of group)
Since question asking largest subgroup size other than 2 , So 7 must be answer.