Chapter 31 - Electromagnetic Oscillations and Alternating Current - Problems - Page 939: 61e

There must be a capacitor in the box.

We can write an expression for the current: $i = I~sin~(\omega_d t-\phi)$ In this case, we can see that $\phi = -42.0^{\circ}$ When $\phi \lt 0$, then $X_C \gt X_L$ Therefore, the circuit is largely capacitive. Since the circuit is largely capacitive, there must be a capacitor in the box.