You use a line of best fit for a set of data to make a prediction about an unknown value. The correlation coefficient for your data set is 1. How confident can you be that your predicted value will be reasonably close to the actual value?
a. I can't be confident at all; this is about as close to a random guess you could get
b. I can be a little confident; it might be close, or it might by way off
c. I can be very confident; it will be close, but it probably won't be exact
d. I can be certain that my predicted value will match the actual value exactly