How are the lower and upper limits of your target heart rate range defined? a. ranging from 50% to 90% of your maximum heart rate. b. subtracting your age from your maximum heart rate. c. taking a pulse in the first and last ten minutes of a workout. d. ranging from 30% to 70% of your maximum heart rate.

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.