Jeffe is explaining dimensional analysis to a friend. he says that dimensional analysis can be used to convert between units. what is needed for this conversion?

The choices can be found elsewhere and as follows:

a. an understanding of significant figures in metric units 
b. an understanding of the difference between accuracy and precision of units 
c. an equality that tells how much of one unit is equal to another unit 
d. an algebra book that explains how linear equations can be set up with units

I believe the correct answer is option C. The important thing in this conversion is an equality that tells how much of one unit is equal to another unit. 

Answer;

An equality that tells how much of one unit is equal to another unit

Explanation;Dimensional analysis refers to the process of conversion between various units. It involves creation of a conversion ratio which has the units required as the numerator and those that exist in the denominator. Conversion of units is very important as the rest of the world uses the metric system.  Unit analysis involves multiplying a given measurement by a known proportion or ratio to give a result with a different unit or dimension.

A.(nh4)(2co3)is the correct answer