Why is circulation in humans called closed double circulation?

Other than earth, is also known to have magnetic pole reversal? a: venus b: mars c: earths moon d: the sun

The ancestors of plants that lived in water had plenty of water for the young. angiosperms are a group of land plants that evolved a reproductive trait for living on land. this trait protect young plants by allowing them to grow only when water is present and the conditions for healthy development are right. what trait most likely young angiosperms in this way?

Pink fur (p) is dominant to purple fur (p) in hamsters. two heterozygous pink hamsters are crossed. what is the probability that these two parents will have an offspring with purple fur? 2/4, 1/2 or 50% 1/4 or 25% 3/4 or 75% 4/4 or 100% there is no chance for this type of offspring