The circled portion of DNA labeled X in the following picture is a a phosphate group
b sugar
c nucleotide
d aldehyde base

The vaccine in a flu shot contains weakened flu viruses. how does a flu shot work with the immune system? a. it destroys lymphocytes. b. it destroys macrophages. c. it activates macrophages. d. it activates lymphocytes.

Which of the following statements is accurate about evolution? question 10 options: natural selection only eliminates odd individuals. evolution means that a population never has changes in its genetic frequencies. mutations are always harmful. evolution means that a population undergoes changes in its gene frequencies over time.

According to theories of how life began, how did early organic molecules begin to separate from the outside world? a: specialized enzymes were required b: chains of amino acids created a barrier c: formation of microspheres or vesicles d: rna catalyzed the formation of membranes