By increasing the circuits resistance r, in a capacitive circuit the phase difference between the current in the circuit and potential difference across the source.
a. gets larger
b. gets smaller
c. remains unchanged
d. depending on the values could get smaller or larger
e. none of these

B) Gets smaller

Explanation:

The difference of phase between current and voltage in a AC circuit is the phase  angle and it depends on the value of Z ( circuit impedance)

Z = R + X   where R is the resistive component and X the reactance component, which is due either to a presence of an  inductor or a capacitor. In any case the total impedance depends on R the resistive, and the phase angle φ is:  

tan⁻¹ φ =  X/R

Have a look to a pure capactive circuit (we are talking about AC current) in this case current leads voltage by 90⁰. If we add a resistor in the circuit  the current still will lead a voltage but in this condition the phase angle will be smaller,

If  R increase, X/R  decrease and tan⁻¹ φ also decrease