Step 1: Understanding the Concept:
This question tests the use of prepositions of time. The correct preposition must indicate that an event happened within a specific period.
Step 2: Detailed Explanation:
The phrase "our holidays" refers to a period of time. We need a preposition that means 'throughout the whole of a period of time' or 'at some point in a period of time'.
- (A) on: Used for specific days and dates (e.g., on Monday, on July 4th). Incorrect.
- (B) at: Used for specific times of the day (e.g., at 5 PM) or for holiday periods when seen as a point in time (e.g., at Christmas), but 'during' is better for the whole duration.
- (C) by: Used to indicate a deadline (e.g., by Friday). Incorrect.
- (D) during: Used to specify that something happens within a particular period of time. "During our holidays" means at some point within that time. This fits perfectly.
Step 3: Final Answer:
The preposition 'during' is correctly used to refer to events happening within a span of time like a holiday. Therefore, option (D) is correct.