Which statement best describes how Watson and Crick's model used other scientists' work to create a model of DNA? A. They used Chargaff's rule to determine that it contains ribose sugar.
B. They used Franklin's photo to determine that DNA was a double helix.
C. They used Levene's work to determine the number of base pairs in each strand.
D. They used Nirenberg and Matthei's studies to determine that DNA is made of nucleotides.

The negative impacts of nonnative species generally outweigh the positive impacts

This is a typical grassland food web. it is also a small picture of an important cycle on earth: the carbon cycle. describe how the carbon gets into this food web. a) bacteria and fungi, the decomposers, recycle carbon from dead organisms. b) carbon is found in the grass and is passed from one level to the next in this food web. eliminate c) all living things give off carbon dioxide as a by-product of respiration and it is released into the atmosphere. d) plants use carbon dioxide as a reactant in photosynthesis, to make usable chemical energy in the form of a sugar.

Which is an example of a vestigial structure? a: paw of a lionb: wing of a birdc: appendix of a humand: tail of a cat(i think it's a but i'm not sure)