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 answer is: "After nearly three weeks, I unexpectedly ran into my manager during a business conference."

Step-by-Step Explanation:

1. Identification of the Error:
The sentence contains a grammatical error involving redundancy (tautology).
The phrasal verb "run into" inherently means to meet someone by chance or unexpectedly.
Placing the adverb "unexpectedly" directly before "ran into" repeats the same meaning unnecessarily, making the expression redundant.

2. Corrected Version:
To fix the error, remove the redundant word "unexpectedly":
"After nearly three weeks, I ran into my manager during a business conference."

3. Review of the Other Options:
- "Intermittent fasting can produce varying effects on fitness depending on individual habits." — This sentence is error-free; the modal verb, modifier placement, and word choice are used correctly.
- "Several towns can promote eco-tourism since numerous residents are keen on hosting guests." — This sentence is error-free; subject-verb agreement and the phrase "keen on" are correct.
- "There are an unknown number of minor asteroids drifting around the planet." — This sentence is error-free; sentence structure and agreement follow standard rules.

Thus, the sentence containing a grammatical error is "After nearly three weeks, I unexpectedly ran into my manager during a business conference."