Wargames Gallery: Target Priority?

What would you do? What are your target priorities?

Here's the situation:

Left to Right Status:

(1) Alpha Legion Heavy Support Squad. 5x Missile Launchers. [No wounds taken all game long].

1x Master of Signals. [No wounds taken all game long].

(2) World Eaters Tartaros Terminators:
2x combi-bolter and chainfist [No wounds taken]

1x combi-bolter and power maul [1 wound remains]

1x Sergeant with thunder hammer (counts as). [1 wound remains]

[This squad started at 10 strong]

(3) World Eaters Leviathan Dreadnought with storm cannon and grav-flux bombard. [5 wounds remain]. The Leviathan is sat (literally) on top of an objective. 

(4) Alpha Legion Tactical Support Squad. 2x Melta Guns [Squad was 5 strong at the start of the game]

1x Alpha Legion Centurion with Power Fist and bolt pistol [No wounds taken all game long]

It is the Alpha Legion's turn. They are at the start of the shooting phase. No World Eaters reactions remain having used them up in the movement phase at the approach of the melta gun squad. The missile launchers have not moved. 

What would you do??!!??