Fill in the blanks with appropriate prepositions from among the choices given below them: People will have to walk _____ the stream to reach the highway.

"Across" is the most suitable preposition to convey the intended meaning of walking from one side of the stream to the other to reach the highway. Therefore, the correct choice is (b) across. (a) among: This preposition suggests being surrounded by or in the midst of a group. However, it doesn't convey the idea of moving from one side to the other, which is the context of walking across the stream. (b) across: This is the correct preposition in this context. It indicates movement from one side of an area to the other, which aligns with the idea of walking across the stream to reach the highway. (c) at: This preposition typically indicates a location or position, but it doesn't convey the idea of moving across the stream. (d) for: This preposition is used to express purpose or reason, and it doesn't fit the context of describing the direction of movement across the stream.