Answer:
Option 3
Step-by-step explanation:
Looking on both sides of the equation you can see that there are 2 moles of lithium chloride (LiCl) and 1 mole of chlorine (Cl2).
In this specific example, you are looking at the numbers in front of the compounds and seeing if they are appropriate, to see if they match what you see in the equation.
So for option 4, it says that there are 2 moles of bromine (Br2) for every 1 mole of chlorine (Cl2), but if you look at the equation there is only 1 mole of Br2 and 1 mole of Cl2, not 2 moles of Br2. (Don't get confused by the subscripts! Only look at the big coefficients in the front for this!)
The same logic applies to options 2 and 1. So only option 3 is feasible.