Select the most appropriate option to substitute the highlighted segment in the given sentence.
My friend has been a teacher since 10 years.

Correct option is A

The correct substitution of the highlighted words is (a) for 10 years.
Explanation: With present perfect (continuous) forms like “has been,” we use for + a period of time (duration) and since + a point in time (starting point). “10 years” is a duration, so “for 10 years” is correct. “Since 10 years” is incorrect because since cannot be followed by a bare duration; it must take a specific time-point such as “since 2015” or “since last January.”
Grammatical rule used:
· for + duration (e.g., for two hours, for three days, for 10 years)
· since + starting point (e.g., since Monday, since 2015, since childhood)
· Example: She has lived in Delhi for five years. / She has lived in Delhi since 2020.
· Information booster: In patterns like “It’s been ten years since…,” since is correct because it introduces a clause with a time-point: “It’s been ten years since she started teaching,” but when the time expression stands alone as a duration, use for.