In: Advanced Math
(a) Show that a group that has only a finite number of subgroups must be a finite group.
(b) Let G be a group that has exactly one nontrivial, proper subgroup. Show that G must be isomorphic to Zp2 for some prime number p. (Hint: use part (a) to conclude that G is finite. Let H
be the one nontrivial, proper subgroup of G. Start by showing that G and hence H must be cyclic.)