One hypothesis in the barn-swallow study was that long-tailed swallows would produce more offspring than average-tailed swallows. which would represent the control group used to test this hypothesis? the swallows with darker-colored tails the swallows with shorter-than-average tails the swallows with longer-than-average tails the swallows with average-length tails

This is the correct answer, I even provided proof from my own test. Hope this helps!

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the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.