The answer is:
C. He believes that his wife is overreacting to the wallpaper.
The importances of the exceprt relies on this words "I don’t care to renovate the house just for a three months’ rental.”a
In that sentence the character lets you know that everything that they consider ugly or not suitable from the house is irrelevant giventhe fact that in three months they will be leaving the house, and by that he states that his wife is over reacting to something that they only have to deal with for a few months.