D

In an LCR series circuit, the potential difference across the resistor (R) and the capacitor (C) has a phase difference of \frac{\pi}{2} (90 degrees). The potential difference across the resistor is in phase with the current, while the potential difference across the capacitor lags behind the current by \frac{\pi}{2}. Therefore, D is incorrect, as it suggests a phase difference when, in reality, these two components have a specific phase relationship.
For the other options, A is correct since the e.m.f. and potential difference across resistance are indeed in phase. B correctly notes the phase difference between the e.m.f. and inductor coil, which is \frac{\pi}{2}. C accurately states that the potential difference at capacitor and inductor have a combined phase difference of also \frac{\pi}{2} when considering the overall phase relationships within the circuit. Thus, D is the wrong statement.