He has saved money because his wife is frugal.

Answer: Option C

Strict : demanding that rules concerning behaviour are obeyed and observed.
Economic : relating to economics or the economy.
Economical : (of a person or lifestyle) careful not to waste money or resources.
Miserly : of or characteristic of a miser.
Frugal : sparing or economical as regards money or food.

Synonym of Frugal is Economical