#### Answer

The sample space is $S=${$HH; HT; TH; TT$}

#### Work Step by Step

During coin flip experiments we use the letter $H$ for heads and letter $T$ for tails.
The sample space is a set that consists of all the possible results of the experiment.
Here, each of the coins can be heads or tails up after landing. Therefore there will be $2\times2=4$ possible outcomes.
The sample space is $S=${$HH; HT; TH; TT$}