STP is standard temperature and pressure being 0C (273K) and 1 atm. For phases of matter we want to look primarily at the temperature part of the definition. Scanning across all the rows we note that most gases are on the right side of the table, let's narrow it down to there. Peering through the groups we find that the halogens are the only group fitting the description with Fluorine and Chlorine being gases, Bromide being a liquid and Iodine and Astatine being solids.
