Which one of the following sentence is correct?

ক. Well, it's many years since we first met. How time does fly!

In this sentence:

- "it's" is a contraction of "it is." The apostrophe indicates the omission of the letter "i." This is the correct form to use when combining "it" and "is."

The rule involves using the appropriate contraction for "it is." In informal and conversational English, contractions are commonly used, and "it's" is the correct contraction for "it is" in this context.

Contrast this with the incorrect options:

- খ. Well, its many years since we first met. How time does fly! - Missing the apostrophe in "its."

- গ. Well, its many years since we first met. How time does fly! - Again, missing the apostrophe in "its."

- ঘ. Well, it many years since we first met. How time does fly? - Incorrect use of "it" without the contraction.

The rule is to use "it's" when combining "it" and "is" in a sentence, and option ক adheres to this rule.