Answer:
C. proportion
Explanation:
It is statement of equality of two ratios
A. fraction
B. ratio
C. proportion
D. rate
(I think the word should be "equality", not "quality".)
The ratio of a to b can be written as:
a to b, a:b, a/b
When you set a ratio equal to another ratio, then you have a proportion.
If ratio a/b is equal to ratio c/d, then you can write
a/b = c/d,
and now you have a proportion.