On the fifth clock pulse, a 4-bit Johnson sequence is $Q_0 = 0, Q_1 = 1, Q_2 = 1,$ and $Q_3 = 1$. On the sixth clock pulse, the sequence is ________.
- $Q_0 = 1, Q_1 = 0, Q_2 = 0, Q_3 = 0$
- $Q_0 = 1, Q_1 = 1, Q_2 = 1, Q_3 = 0$
- $Q_0 = 0, Q_1 = 0, Q_2 = 1, Q_3 = 1$
- $Q_0 = 0, Q_1 = 0, Q_2 = 0, Q_3 = 1$