The correct answer is C. Zero.
An ammeter is a device used to measure electric current. It is connected in series with the circuit being measured, so it must have a very low resistance to avoid affecting the current being measured. An ideal ammeter would have zero resistance, but this is not possible in practice. The resistance of an ammeter is always non-zero, but it should be as low as possible to minimize the error in the measurement.
Option A is incorrect because a low resistance ammeter would draw a large current, which could damage the ammeter or the circuit being measured.
Option B is incorrect because an infinite resistance ammeter would not allow any current to flow through it, and so it would not be able to measure the current.
Option D is incorrect because a high resistance ammeter would affect the current being measured, and so it would not be an accurate measurement.