Explanation: An AC ammeter indicates the **Effective (RMS) values of current**. Here's why: Alternating current (AC) constantly changes direction and magnitude. The Root Mean Square (RMS) value is the standard way to quantify AC because it represents the "effective" current. This means that an RMS current will produce the same heating effect in a resistive load as a DC current of the same magnitude. For a pure sine wave, the RMS value is approximately 0.707 times the peak value. * **A) Effective (TRM) values of current:** "TRM" is not a standard electrical term. While meters can be "True RMS" (accurate for non-sinusoidal waveforms), "effective" is a description of RMS, not a separate unit. * **C) Peak values of current:** Peak current is the maximum instantaneous value. While important for voltage breakdown or transient analysis, it doesn't represent the continuous power delivery that an ammeter typically measures. * **D) Average values of current:** For a symmetrical AC waveform, the average current over a full cycle is zero, as the positive and negative halves cancel out. This wouldn't be useful for measurement.