Gamete cells contribute to offspring because through meiosis, haploid cells with half of the chromosomes are created. They increase genetic variation by combining with the cell from the other organism. This contributes to offspring because they get good traits from both parents rather than being genetically identical to just one.
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A and C are the same and thus both wrong. B. The higher the temperature, the more molecules start moving, the more space inbetween them and thus the larger.