With this being a global question (no additional information such as what if P is 3rd, etc) you could wait to do these at the end of the game. You would have previous work from other questions to easily answer this.
However, you can still knock this one out by looking at our global diagram. We can expect the test writers to really test restrictions with our sequencing tree that we have assembled.
So who could not be 3rd? The most attractive candidate to consider is F. Look at how many variables must follow F.
If F went third, then G must be fourth (as G must be exactly one of three or four). We now have two spaces left to place the three variable sequence of L-M-H. We do not have room. This is what is to be expected on sequencing games. F is our answer.