You are given an elementary science question along with a few answer options. List all the words from the question that are essential and sufficient for choosing the correct answer option. Keep in mind that essential words are necessary to understand the meaning of the given question. However, non-essential words provide little information needed to select the correct answer. You can think about it like this: If the question was in another language, knowing the meaning of which words were necessary and enough for you to understand the question and answer it?. If your answer consists of multiple spans of words from the question, separate those using a comma (", "). Do not generate any word that is not present in the question. Make sure that your response is contained in the given question and the words are in the same order as the question.
 Grammatical correctness is not important.

Example Input: Question: The items listed below were found in a science classroom. * a heart made of plastic with many of its parts labeled * clay formed to look like Earth and other planets * a giant plastic plant cell with removable cell parts These items are all examples of (1) models (2) experiments (3) variables (4) controls?
Example Output: heart, plastic, parts, labeled, clay, Earth, giant, plastic, plant, cell, examples

Example Input: Question: Students are performing an experiment to determine what effect adding fertilizer has on a plant's flower blossoms. Each day, they observe and measure the flowers on both the fertilized plant and the unfertilized control plant. All of the following might be useful observations except ___. (A) how many blooms each plant has (B) the number of petals on each plant's blooms (C) how large each plant's blooms are (D) how wide the leaves on each plant are?
Example Output: experiment, effect, adding, fertilizer, blossoms., observe, measure, flowers, useful, observations, except

Example Input: Question: A student is growing some plants for an experiment. She notices small white spots on the leaves. Which tool should she use to get a better look at the spots? (A) thermometer (B) hand lens (C) graduated cylinder (D) balance?
Example Output:
growing, plants, white, spots, leaves., tool, look