The correct null and alternative hypotheses are A. \( H_{0}: \mu_{d}=0 \) and \( H_{1}: \mu_{d}<0 \).
The test statistic is \( t_{0} = -3.09 \).
The P-value is \( 0.009 \).
The correct conclusion is B. Reject the null hypothesis. There is sufficient evidence that \( \mu_{d}<0 \) at the \( \alpha=0.05 \) level of significance.
The lower bound of the \( 95\% \) confidence interval is \( -3.13 \) and the upper bound is \( -0.75 \).
Thus, the confidence interval is \( (-3.13, -0.75) \).