Which measure is equivalent to 2.5a) 2.5 mlb) 250 mlc) 2500 mld) 25000 ml

option C) 2,500 ml (under the assumptions shown below)
Explanation:

This is a conversion of units, but you missed the unit of the question.

What is it? 

It seems it should be 2.5 liters.

So, I am going to explain you how to deal with this problem, assuming you have to find the measure equivalent to 2.5 liters.

All the choices are in mililiters (ml).

Then, you use the conversion factor 1 liter = 1000 ml

With that you do:

2.5 liter × 1000 ml / liter = 2,500 ml

And that is the choice C).