Let H={±1,±i} be the subgroup of G=C∗ of fourth roots of unity. Describe the cosets of H in G explicitly. Is G/H isomorphic to G?
a) Cosets: {1,−1},{i,−i}; Isomorphic: Yes
b) Cosets: {}, {1, -1, i, -i}; Isomorphic: No
c) Cosets: {1, -1, i, -i}, {}; Isomorphic: Yes
d) Cosets: {1, -1}, {i, -i}; Isomorphic: No