The following atoms are all variations of the element carbon: 12c, 13c, and 14c due to differing numbers of neutrons. what are these variations called?
a. isomers
b. isotopes
c. molecules
d. polymers

What does it mean for a cell membrane to be selectively permable

What pattern of migration do whales follow?

19. a cell is viewed under a microscope and is found to have two nuclear envelopes and spindles that appear to be breaking apart. which phase of mitosis is the cell most likely in? a. metaphase b. prophase c. telophase d. anaphase