Option 1 -> Represents new admissions during the session - a flow measured over a period of time.
Option 2 -> Represents number of boys at end of session - a stock measured at a point in time.
Option 3 -> Represents total students on 1st April 2023 - a stock measured at a point in time.
Option 4 -> Represents total students at end of session - a stock measured at a point in time.
Hence, Option 1: 186 -> A flow variable is measured over a period of time and represents change or movement. The 186 new admissions occurred during the session (over a period), making it a flow variable. In contrast, options 2, 3, and 4 are stock variables as they represent quantities at specific points in time (snapshots). Similarly, the 43 withdrawals would also be a flow variable, but it's not among the options. -> correct