Explanation:

The correct answer is option 'C': in / at.

Explanation:
To determine the correct prepositions to use in this sentence, we need to consider the context and conventions of the English language.

In / at:
The preposition "in" is used to indicate a general time period or a larger span of time, such as days, weeks, or months. On the other hand, the preposition "at" is used to indicate a specific time or a particular point in time.

Afternoon / Night:
In this sentence, we are given two time periods: afternoon and night. The word "afternoon" refers to the time period between noon and evening, while the word "night" refers to the time period between sunset and sunrise.

Using the correct prepositions:
To determine the correct prepositions to use with these time periods, we need to consider their nature and how we typically refer to them in English.

- In the case of "afternoon," it is more appropriate to use the preposition "in" because it refers to a general time period. We often say "in the afternoon" to indicate that something will happen during that timeframe. Therefore, we should use "in" before "the afternoon" in the sentence.

- Similarly, in the case of "night," it is more appropriate to use the preposition "at" because it refers to a specific point in time. We often say "at night" to indicate that something will happen during the nighttime. Therefore, we should use "at" before "night" in the sentence.

Final Answer:
Therefore, the correct prepositions to use in this sentence are "in" before "the afternoon" and "at" before "night." Hence, the correct answer is option 'C': in / at.