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Two $D$-flip-flops, as shown below, are to be connected as a synchronous counter that goes through the following $\mathrm{Q}_{1} \mathrm{Q}_{0}$ sequence $00 \longrightarrow 01 \longrightarrow 11 \longrightarrow 10 \longrightarrow 00 \longrightarrow \dots$
The inputs $D_{0}$ and $D_{1}$ respectively should be connected as

1. $\overline{\mathrm{Q}_{1}}$ and $\mathrm{Q}_{0}$
2. $\overline{\mathrm{Q}_{0}}$ and $\mathrm{Q}_{1}$
3. $\overline{\mathrm{Q}_{1}} \mathrm{Q}_{0}$ and $\overline{\mathrm{Q}_{1}} \mathrm{Q}_{0}$
4. $\overline{\mathrm{Q}_{1}} \; \overline{\mathrm{Q}_{0}}$ and $\mathrm{Q}_{1} \mathrm{Q}_{0}$