The correlation coefficient "r" of a group of paired data (x,y) is a number that measures how much the data follows a linear model. This number has the following property:
This means that it can only take values between -1 and 1, therefore options A, and D is not possible. When r = 1, this is a total positive linear correlation, and when r = -1 this is a total negative linear correlation. Positive linear correlation means that the data follow a linear model with a positive slope, that is the values of "y" increase in the positive direction as the values of "x" increase.
In this case, the altitude is the independent variable, therefore is analogous to "x", and the temperature is the dependent variable, therefore analogous to "y".
We see that as the values of "x" increase, the values of "y" decrease, therefore is a negative linear correlation therefore "r" must be smaller than zero. Therefore the only possible answer is -0.99