The percentage of the variability in humidity level explained by its relationship with temperature is 73.84%. Option B is the correct answer.
The percentage of the variability in humidity level explained by its relationship with temperature is given by the coefficient of determination, which is the square of the multiple correlation coefficient (R).
In this case, the R Square value is 0.7384, so the percentage of the variability in humidity level explained by its relationship with temperature is 73.84%. Therefore, the correct answer is: 73.84%. Option B is the correct answer.