A coin is tossed three times, if the event E is such that " head on third toss" then it's sample space will be-

{(HHT), (HTH), (THH), (TTH)} {(HHH), (HTH), (THH), (TTH)} {(HHH), (HTH), (THH), (TTT)} {(HHH), (HTT), (THH), (TTH)}

{(HHH), (HTH), (THH), (TTH)}

If a coin is tossed three times, the sample space S is = {(HHH), (HHT), (HTH), (HTT), (THH), (THT), (TTH), (TTT)} Now the sample space for the event E such that "head on third toss" = {(HHH), (HTH), (THH), (TTH)}