A student titrated a solution containing a mono-protic acid to determine its concentration. A standardized NaOH solution was used as the titrant. The teacher informed the student that the value he obtained for the concentration was high. Which of the following could account for the enlarged value?
I. The student passed the endpoint of the titration.
II. The student rinsed the buret with distilled water, and then filled it with the NaOH solution.
III. The student did not rinse the side of the Erlenmeyer flask with distilled water during the titration.
(A) I only
(B) II only
(C) I and II only
(D) I, II, and III

I. Passing the endpoint of the titration could result in an incorrect determination of the concentration because it means the student added more titrant (NaOH) than necessary to neutralize the acid. This would lead to an overestimation of the acid's concentration.

II. Rinsing the buret with distilled water and then filling it with the NaOH solution could introduce additional water into the NaOH solution, diluting it. As a result, the volume of NaOH solution added during the titration would be greater than intended, leading to an overestimation of the acid's concentration.

III. Not rinsing the Erlenmeyer flask with distilled water during the titration might introduce a small error in the volume measurement due to the presence of solution droplets clinging to the sides. However, this would not significantly affect the concentration calculation compared to the errors caused by passing the endpoint or diluting the NaOH solution. Therefore, this factor alone is less likely to account for the enlarged value.

Therefore, options I and II are the most likely reasons for the high concentration value obtained by the student.