Fill in the blank with a suitable preposition.
She painted the picture _______ the competition.
The preposition ‘for’ is used to denote reason or purpose. In the given sentence the person is painting because of the competition. Therefore option C is correct. Whereas ‘within’ and ‘to’ are used to denote a place or moving to a place respectively. Since both of these prepositions are inappropriate to the given context, options B and D are incorrect. On the other hand ‘with’ is used to refer to a tool or the company of someone. In the sentence ‘the competition’ is neither of these thus option A is incorrect.