In each of the questions given below, four sentences have been given. Out of four sentences, one sentence has an error. Find out which of the following sentence has an error. If all the given sentences are error-free then choose option ‘ All are correct’ as your answer choice.

Which of the following sentences contains a grammatical error?

The correct option containing the grammatical error is: After nearly three weeks, I unexpectedly ran into my manager during a business conference.

Let's analyze the given sentences step-by-step to identify the sentence with an error:

1. "Intermittent fasting can produce varying effects on fitness depending on individual habits."
This sentence is grammatically correct. The subject and verb agree, and the prepositional structures are used properly.

2. "Several towns can promote eco-tourism since numerous residents are keen on hosting guests."
This sentence is grammatically correct. The subordinating conjunction "since" correctly connects the main clause to the causal clause.

3. "After nearly three weeks, I unexpectedly ran into my manager during a business conference."
This sentence contains a grammatical/contextual error. The introductory prepositional phrase "After nearly three weeks" is incomplete because it lacks a reference point or object of time duration (e.g., "After nearly three weeks of vacation" or "After nearly three weeks had passed").

4. "There are an unknown number of minor asteroids drifting around the planet."
This sentence is grammatically acceptable as structured.

Therefore, the sentence that contains the error is: After nearly three weeks, I unexpectedly ran into my manager during a business conference.