Choose the correct Preposition that should be inserted in the blank :…

The correct answer is Option (4) → since

Complete sentence: The school was not far from my home and I used to walk, but since the start of last year I had been going with the other girls in a rickshaw and coming home by bus. The action "had been going" in a rickshaw began at a point of time, the start of last year, and went on after it. So "since the start of last year I had been going ...".

Option	Used to show	Example
(1) for	For is used with a period of time (for two years, for a month), not with a point of time such as "the start of last year".	He has lived in Delhi for ten years.
(2) before	"Before the start of last year" would mean the rickshaw rides happened earlier than that point, which does not fit "had been going" continuing from it.	Finish your homework before dinner.
(3) from	From also marks a starting point, but it usually pairs with to / till (from Monday to Friday). An action that began at a point of time and continued (perfect continuous "had been going") is joined to that point by since.	The shop is open from nine to five.
(4) since (answer)	Since marks the point of time at which an action began and continued up to a later time. It is used with the perfect and perfect continuous tenses (have been going, had been going).	She has been learning music since the age of six.