PLEASE HELP ASAP 50 POINTS AND BRAINLIEST EASY QUESTION!

Which options have a unit rate of 3?

1. 3 3/4 : 2

2. 2 : 2/3

3. 15/2 : 2 1/2

4. 2 1/2 : 5/6

5. 1 : 1/4

6. 2/3 : 1

PLEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEASE!