The semilunar valves prevent the backflow of blood into the atria when the ventricles are contracting. the semilunar valves prevent the backflow of blood into the atria when the ventricles are contracting. a. true b. false

Molecular models of two different substances are shown below. in the molecule on the left, the oxygen atom pulls on electrons more strongly than the hydrogen atoms. in the molecule on the right, the two oxygen atoms pull on the shared electrons with the same strength. water molecule, h,o oxygen molecule, oz when the two substances are put in the same container, they do not attract each other. why does this happen? a. they both contain oxygen. b. one is polar and one is nonpolar. c . they are both polar. d. they contain different elements.

Read each description below and determine to which stage of sleep each pertains. then click and drag each box into the appropriate category below.

In one or two well-crafted paragraphs in your laboratory journal, summarize the process in which normal cells become cancer cells. your paragraph(s) must include each of the terms listed below. underline each term in your writing: