The question requires us to provide the expected pH of both deionized water (DI water) and a sodium chloride solution, and then compare these information with the experimental data.
a) The pH of deionized water, in theory, should be 7 (neutral medium) because of the lack of ions.
b) The pH of sodium chloride solution should also be 7 (neutral medium), because chlorine ion (Cl-), being the conjugated base of HCl, presents a substantially weak basicity.
c) For DI water and sodium chloride solutim, it was observed an alkaline character, therefore the observations did not agree with the expectations. On the other hand, when tested with phenoftalein indicator and pH test paper, both water and NaCl solution presented clear color, indicating that there wasn't a great deviation of pH from 7.
The difference observed could be explained by the presence of contaminant ions in the water used for the experiment, such as molecules in the air that, when in contact with water, form ions that would affect the pH.