Select the most appropriate option that can substitute the highlighted segment in the given sentence.
I have been calling him from many days.

Correct option is A

The correct preposition to use in this context is "for." The phrase "for many days" properly denotes the duration of time over which the action has been taking place.
· In this context, "for" is used to indicate a period of time during which something happens or continues. It is commonly used with expressions of duration to specify how long something has lasted.
· Example: He has lived in this town for over twenty years.
Meanings of all the other given options:
· About: Pertaining to; concerning something or someone.
· Of: Used to indicate relation, belonging, or possession.
· Since: From a particular time in the past until now, used only with specific starting points.