Answer:
Distribution of question papers is a common practice in educational institutes. The teacher may use different methods to distribute the papers to the students. In this question, the teacher distributed the question papers among the students. Let's discuss the meaning of the collocation "distributed among" in detail.

Meaning of "Distributed Among":
The collocation "distributed among" means to divide something into parts and give each part to a different person or group of people. When we use this collocation, we imply that the distribution was done equally or fairly among the recipients.

Examples:
- The teacher distributed sweets among the children.
- The books were distributed among the students of the class.
- The charity organization distributed clothes among the flood victims.

Explanation of options:
a) Across - This collocation is used to describe something that goes from one side to another side of a place or thing. Example: The bridge goes across the river.
b) Around - This collocation is used to describe something that surrounds or encircles a place or thing. Example: The fence is around the garden.
c) About - This collocation is used to describe something that is approximately or roughly a certain amount or number. Example: There were about ten people in the room.
d) Among - This collocation is used to describe something that is divided equally or fairly among a group of people or things. Example: The prizes were distributed among the winners.

Conclusion:
In conclusion, the teacher distributed the question papers among the students. This collocation means that the distribution was done equally or fairly among the recipients. The other options (across, around, and about) have different meanings and are not suitable in this context.

Answer is d