Answer:
See the attachments
Explanation:
To represent the ratio 4 : 6, the diagram needs to show 4 of some unit against 6 of the same unit. (Each unit represents the same number of students.) The attached diagram is the only one that does that.
_____
The ratio can be reduced to 2 : 3, which the second diagram shows. Since you're asked to choose all that apply, I'd say both the 2nd and 3rd diagrams should be chosen.