The minimum frequency below which no electron is emitted from the metal surface is called:

Explanation

The correct answer is Threshold frequency. This is the minimum frequency of light necessary to eject electrons from a metal surface as described by the photoelectric effect. It varies based on the material of the metal, as different metals have different work functions. Option A, High frequency, is incorrect because it suggests a frequency above the minimum required. Option B, Low frequency, is incorrect because such a frequency would not provide sufficient energy for electron emission. Option D, Resonance frequency, is unrelated to this context as it refers to a system's natural vibration frequency.