The given sentence requires an adverb before the adjective. The combination of the comparative degree of adjectives and 'much' is often used to emphasize the degree of the adjective. Here, 'much' explains how better the situation is this week, hence, Option C is the correct answer.
'Very' is used with the positive degrees of adjective. Here, 'better' is a comparative degree of adjective, hence option A is incorrect.
'Too' is used with the positive degree of adjective too. Hence, option B is incorrect.
'More' is used with the comparative degree of adjectives. It is often used to compare two subjects, as we don't have any subjects to be compared here, it's incorrect. Hence, option D is incorrect.