Answer:
A.
Step-by-step explanation:
In a direct proporton, the ratio of one quantity to teh other is a constant.
Let's divide each number of crystals by each number of pounds:
7/14 = 1/2
14/28 = 1/2
21/42 = 1/2
28/56 = 1/2
The ratio of crystals to pounds is always 1:2.
This is a proportional relation.
Answer: A.
