To find the ratio of the number of students sitting on the floor to the number of students sitting on the bleachers, we have:
- Number of students on the floor = 35
- Number of students on the bleachers = 2
The ratio is calculated as:
\[ \text{Ratio} = \frac{\text{Number of students on the floor}}{\text{Number of students on the bleachers}} = \frac{35}{2} \]
This can also be expressed as 35:2.
So, the correct answer is 35:2.