Please help me a #5

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The organ that has two atria and one ventricle is the

In the diagram below, ab and bc are tangent to o. what is the measure of

Which revelation resulted from the observation of the spectrum of different galaxies? a. there were more galaxies whose spectrum was blueshifted b. there were no galaxies whose spectrum was redshifted c. there were more galaxies whose spectrum was redshifted d. there were no galaxies whose spectrum was blueshifted