Which of the following are stock variable(s)?

(A) Population

(B) Capital formation

(C) Number of students in a school

(D) Change in inventories

Choose the correct answer from the options given below:

Option 1 -> Incorrect. Capital formation is a flow variable, not a stock variable.

Option 2 -> Incorrect. Capital formation and change in inventories are both flow variables.

Option 3 -> Incorrect. Capital formation is a flow variable (addition to capital over time), not a stock variable.

Option 4 -> (A) Population and (C) Number of students in a school are measured at a specific point in time, making them stock variables.

Hence, Option 4: (A) and (C) only -> Stock variables are measured at a particular point in time, representing quantities that exist at that moment. Population is counted on a specific date, and number of students in a school is also measured at a specific point. In contrast, Capital formation (B) and Change in inventories (D) are flow variables as they represent changes or accumulations over a period of time, not at a single point -> correct