Final answer:
The corresponding word problem to Ms. Howe's bar model is C, as it pertains to dividing a rectangle into three equal parts, with two-thirds shaded, and asks for the fraction of the part that is not shaded.
Step-by-step explanation:
The word problem that best corresponds to Ms. Howe's bar model is "C. A rectangle is divided into three equal parts. Two of the parts are shaded, and the remaining part is not shaded. What fraction of the rectangle is not shaded?" This problem directly relates to the model where the whole is represented as an area divided into three equal parts. The shaded portion represents two-thirds of the area (⅓ each), while the non-shaded portion represents the remaining one-third (⅓).
In this problem, the two shaded parts correspond to the two parts of the bar model that are filled, and the one non-shaded part corresponds to the empty part of the model with a question mark. Therefore, the fraction of the rectangle that is not shaded is indeed one-third, which aligns with the model presented by Ms. Howe.