James was observing cells under a microscope. he observed some cells which had a layer outside the plasma membrane. what is this layer called?
a. cell membrane
b. cell wall
c. nuclear membrane

Which of the following was not a major animal on land during the carboniferous period? amphibians insects both a and b none of the above

If a checkpoint detects damaged dna, the checkpoint may

To test the responsiveness of the kidneys, scientists have designed an experiment tracking urine output of people during a normal day, while regulating the in-take of water by mouth. what would be an appropriate hypothesis for this experiment?