B1=L B2=F B3=L B4=F [ 9 ] [37.50%]
B1=L B2=F B3=F B4=F [ 0 ] [0.00%]
B1=L B2=F B3=F B4=L [ 2 ] [8.33%]
B1=L B2=F B3=L B4=L [ 13 ]
It's time for answer, well, everyone is FALSE muahhahahahahahh it is answer 2 (LFFF), let me explain :
the third barrack is lifted, yes marines can't be made with it and marines can walk under it.

good bunker, no ?

here is how you could saw that :

PS : I enlarged the image for your small eyes ;p
now, if you don't believe me :

hehe and for the last barrack, sorry but it was too simple to see it was flying, look the barrack, it has a flying position, how could marines be made with that ? Anyway if you have a glitch to make marines like that, I would correct and 2answers will be correct, but i want the glitch proof

How I made ?!
Simple, I was toying with p14 scanner sweeper lol !
at start get a barrack lifted and land it just at the begining of the game, sometimes, it will really land before freeze if you are not lucky, but you can lift it after the freeze and it will be exactly like a landed barrack without the "proof" in my screenshot other here, but if you are lucky, it will freeze just before it land, and you will have a strange shadow

(like the screenshot) i took the strange shadow to make the game possible

hum now the last barrack, VERY VERY simple, just have a landed barrack at start, wait for freeze and lift it, it will be like this

PS : the time to freeze with p14 is about 3secs or something like this