Which base-pair rules apply to the double helix structure? SELECT ALL THAT APPLY

a. A-G
b. G-T
c. A-T
d. C-G

This is definitely more biology. Double helix represents DNA not RNA.
Adenine always pairs with thymine.
Cytosine will always pair with guanine.
So answers C and D.
The reason they pair together is because of the way they can form hydrogen bonds with one another.

grass

Explanation:

Grass is at the very bottom of the food chain and relies solely on sunlight and water, which aren't organisms. I'm going to assume you meant prairie dog because a prairie isn't an organism, but prairie dogs rely on grass for food. Ferrets rely on meat for food (which they get from other animals) and foxes rely on other animals for food as well. Therefore, grass is the only organism that is a producer (gives other organisms food) and doesn't rely on other organisms for food.