1. The problem statement, all variables and given/known data I do not understand the following statement (Please, see the attachment): "C4 has trivial subgroups and only one cyclic subgroup of 2 elements, namely <b>. This is because both a and c can be verified to be generators of C4." 3. The attempt at a solution The notation <something> is normally used to indicate a generator of a group. However, the paragraph uses the notation only for the cyclic subgroup b such that <b>. The following support statement for the above clause is what I do not understand: "This is because both a and c can be verified to be generators of C4." If a subgroup has a generator, then it is a cyclic group. The paragraph says that the group has two generators, a and c. Then, a and c must be also cyclic subgroups of C4. This is a contradiction to the first clause that C4 has only one generator b. What does the paragraph really mean?