A is incorrect. Eating nothing but fruits will not provide you with the right amount of carbohydrates and proteins everyday. C is incorrect. It is not enough that we eat one of each food group since we have target calories per food group. D is incorrect since calcium is not only what our body needs. B is correct, we have target number of calories each day in our diet.
Answer: 2)
A mnemonic device
Explanation: A mnemonic is a tool or memory aid that helps people to remember or memorize things easily. It helps you to remember an idea or phrase with a pattern of letters, numbers, or relatable associations. Mnemonic devices may include special rhymes and poems, acronyms, images, songs, outlines, and other tools. In the question Luke makes up a sentence using the first letter from each base as the first letters for his words, repeating to himself to help him remember more easily the bases of DNA. In other words Luke formed mnemonics using the first letters of the DNA bases to remember them easily.