Explanation: Blocking oscillators are a type of relaxation oscillator whose timing and frequency are fundamentally determined by the charging and discharging characteristics of a resistor-capacitor (RC) network. The time constant (T) of an RC circuit, which directly governs how quickly the capacitor charges or discharges and thus dictates the oscillation period, is given by the formula T = R × C. Option B, I = E/R (Ohm's Law), describes the relationship between current, voltage, and resistance in a circuit but does not define the dynamic timing mechanism of an oscillator. Option C, referring to a receiver’s AGC (Automatic Gain Control), is incorrect because AGC is a circuit in receivers used to maintain a constant output level and has no relevance to the operation or timing of a blocking oscillator, which is a signal generating circuit. Therefore, D is also incorrect.