Which of the following is an appropriate confidence interval

Which of the following is an appropriate confidence interval to indicate significance for a risk difference of -2.4?

a. -2.5 to 0.67

b. 2.4 to 3.6

c. -2.5 to -1.4

d. -2.5 to 1.9

If test statistic is not in CI, then that test is significant at (1-alpha) level.

b. 2.4 to 3.6