Correct Answer: gain experience

Solution : The fourth option is correct.

When replacing acquire experience with the provided options:

• Gain experience maintains the intended meaning of acquiring knowledge or skills over time. It fits grammatically and expresses the idea clearly.

• Experienced is an adjective and doesn't fit well in the context of the sentence as it doesn't convey the action of acquiring experience.

• Developed experience is less commonly used in this context and might be considered slightly awkward.

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• Got experience is less formal and might be considered more colloquial. "Got" is a casual term that might not be suitable for a formal context.

Therefore, " Old people gain experience through age " is the most suitable answer.