The resistance of an ideal ammeter is-

The correct answer is Option (3) → zero

An ammeter is connected in series, so its own resistance adds to the circuit and lowers the current it is meant to measure. An ideal ammeter changes nothing, which needs zero resistance. A real ammeter has a very small resistance (a galvanometer with a low shunt).

NCERT (2026-27):
The Moving Coil Galvanometer – “… (ii) For measuring currents, the galvanometer has to be connected in series, and as it has a large resistance, this will change the value of the current in the circuit.”

The Moving Coil Galvanometer – “… (c) For the ideal ammeter with zero resistance, I = 3/3 = 1.00 A”