What is the sample space when a coin is tossed twice?

Question

Responses
A {H, T}{H, T}
B {HH, HT}{HH, HT}
C {HH, TT, TH}{HH, TT, TH}
D {HH, HT, TT, TH}

Answer 1

D {HH, HT, TT, TH}