Step 1: Understanding Prepositions of Time:
The preposition "since" is used when referring to the starting point of an action that continues to the present. It is used with a specific point in time, like "childhood" in this sentence. Step 2: Analyzing the Options:
- In: This is incorrect because "in" is used for general periods like "in the morning" or "in the past."
- For: This is used for a period of time (e.g., "for two years") and not for a starting point.
- At: This is used for specific points of time (e.g., "at 5 PM"), but it doesn't fit with "childhood" in this context.
- Since: This is the correct option because "since" is used with a specific starting point, like "childhood." Step 3: Conclusion:
The correct preposition is since.