Which of the following statements about sleep is true? a. sleep is a uniquely human phenomenon. b. sleep is a state of consciousness. c. sleep is needed for digestive health. d. sleep is likely a social invention.

What parts of the cardiovascular system are affected with atrial fibrillation?

During the first month of development, how many layers of cells make up the embryo? a. 1 b. 2 c. 3 d. 4

What is the main structural difference between enveloped and nonenveloped viruses? a) enveloped viruses have their genetic material enclosed by a layer made only of protein.b) nonenveloped viruses have only a phospholipid membrane, while enveloped viruses have two membranes, the other one being a protein capsid.c) enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.d) both types of viruses have a capsid and phospholipid membrane; but in the nonenveloped virus the genetic material is between these two membranes, while in the enveloped virus the genetic material is inside both membranes.