A researcher uses a within-subjects design in which one group completes a difficult puzzle and the second group completes an easy puzzle. He finds that participants who completed the difficult puzzle first were able to learn about the puzzle and completed the easy puzzle quicker, compared to participants who did the easy puzzle first. What type of threat to internal validity was described in this example

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the answer is "meiosis ii in the mother".

the procedure of meiosis includes two divisions of the hereditary material. the main division is known as the decrease division – or meiosis i – on the grounds that it lessens the quantity of chromosomes from 46 chromosomes or 2n to 23 chromosomes or (n depicts a solitary chromosome set). in people, the decrease division results in two sperm cells each with 23 chromosomes or an egg cell with 23 chromosomes and one disposed of polar body. the second division – or meiosis ii – is called equational division. the two sperm cells split again creating four sperm cells, each with 23 or n chromosomes. in oogenesis, the egg cell and polar body partition to shape the ovum and two extra polar bodies. along these lines, the posterity are guaranteed to get one portion of the chromosomes from the mother and one half from the dad.

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