Because 0 is not in the interval (0.07, 0.19). It is unlikely to be the true difference between the proportions. III is just plain wrong! We cannot make a probability statement about an interval we have already constructed. All we can say is that the process used to generate this interval has a 0.95 chance of producing an interval that does contain the true population proportion. 
A 95\% confidence interval for the difference between two population proportions is found to be (0.07, 0.19). Which of the following statement is (are) true?  I. It is unlikely that the two populations have the same proportions.  II. We are 95\% confidence that the true difference between population proportions is between 0.07 and 0.19.  III. The probability is 0.95 that the true difference between the population proportions is between 0.07 and 0.19. 
Options:
a. I 
b. II 
c. I, II 
d. I, III 
e. II, III 