Answer: Option (b) is the correct answer.
Step-by-step explanation:
The given reaction is as follows.

Also, it is given that 8 moles of lithium metal on reaction with excess of oxygen results in the formation of lithium oxide.
Let the number of moles of lithium oxide is x. 4 lithium atoms give 2 atoms of lithium oxide, therefore, divide the number of moles of lithium by half as follows.
Number of moles of lithium = number of moles of lithium oxide
8 = 2x
or, x =

x = 4
Thus, we can conclude that when 8 moles of lithium metal react with excess oxygen gas, then 4 moles of lithium oxide can be produced.