Institution: PROBASHI KALLYAN BANK Exam: প্রবাসী কল্যাণ ব্যাংক-সিনিয়র অফিসার-09-10-2021
Topic: Substitution, Expression, & Definition, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The phrase "to call it a day" is an idiomatic expression that means to stop working for the day or to conclude an activity, usually when one feels that they have done enough or when it is no longer productive to continue.

When we break down the options provided:

- **A) to quit**: This directly aligns with the meaning of the idiom, as it signifies ending work or ceasing an ongoing task.

- **B) it becomes evening**: While this option suggests a time-related context, the phrase is not specifically tied to the time of day but rather to the conclusion of activities.

- **C) to say good morning**: This phrase does not relate to the context at all, as it refers to beginning the day rather than ending it.

- **D) to start**: This again contradicts the idiom’s meaning, as it implies an initiation, not a cessation of activity.

In summary, option A is correct because "to call it a day" succinctly encapsulates the idea of quitting or wrapping up one’s efforts, making it the most fitting choice among the given options.