Fill in the blank with a suitable preposition.
Skye realized that she needs to buy a new sweater for winter ________ the end of summer.
The prepositions ‘on’ and ‘upon’ are both used to speak about placing something over something else. ‘On’, as a preposition of time, is also used to denote a day or date. Since ‘the end of summer’ is neither a place/surface nor a day/date the prepositions ‘on’ and ‘upon’ are both unsuitable. Thus options A and D are incorrect. On the other hand, ‘for’ is used to denote a reason for something. If we use ‘for’ in the sentence, the meaning of the sentence changes. It conveys that Skye is purchasing the sweater to wear during the end of summer, and not for winter. Thus option B is incorrect. The preposition ‘towards’ is used to speak about being close to a point in time. In the given context, the end of summer can also be interpreted as being close to winter. Thus option C is correct.