The octet rule tells us that for an atom and a bond to be stable there must be 8 electrons in its last energy level, in other words it must have 8 valence electrons.
Now, if we look at the structure of PCl3 we can see that it complies with the octet rule as shown in the following figure:
Each line corresponds to two electrons and the dots correspond to one electron each. We have 3 lines (6 electrons) and two dots (2 electrons) for a total of 8 electrons.
Now for H2S we have, see the figure above. We have 2 lines (4 electrons) and four dots (4 electrons) for a total of 8 electrons.
For SF6 we have, see the figure above. For SF6 we have six lines (12 electrons), that is to say, that this is the compound that does not fulfill the octet rule.
The answer will be SF6