Correct option is A. same
For example:
To express the ratio of $$1$$ metre : $$200$$ cm, both the quantities have to expressed in same units.
Ratio of $$1$$ metre : $$200$$ cm $$= 100$$ cm : $$200$$ cm
$$= 1 : 2$$
$$\therefore \textbf{To find the ratio of two quantities, they must be expressed in same units}$$.