Explanation:

- Quantitative measures/instruments of monetary policy, like bank rate, open market operations, and cash reserve ratio, control the overall supply or quantity of money in the whole economy.

- Option 1: Controlling money across "selected sectors" refers to *qualitative* or selective instruments, not quantitative ones.

- Option 2: Correct. Quantitative measures aim at controlling the quantity of money in the entire economy.

- Option 3: Partially correct—the ultimate target of these policies can be inflationary or deflationary gaps, but the direct focus is on the overall money supply, not just price gaps.

- Option 4: Incorrect, because only Option 2 clearly fits.

Correct answer: Option 2, "Quantity of money in the economy."