Which of the following statements are true?
i. each white blood cell contains millions of hemoglobin molecules.
ii. in a sample of blood, there are more red blood cells than white blood cells.
iii. hiv destroys red blood cells.
iv. all blood cells come from one pool of stem cells.
a. ii and iv only
b. i and iv only
c. ii and iii only
d. i, iii, and iv only
e. i, ii, and iv only

An easy way to calculate the amount of energy available at each level is to what?

According to piaget, children have acquired the cognitive skill of conservation when they're able to a. understand that six ounces of liquid in a jar and six ounces in an elongated tube are equal. b. understand the viewpoint of other people. c. relate objects around them to their own needs. d. realize that the term heavy describes an object one way and the term big describes it another way. it is not b nor c. did this 2 x wrong..

Which would best keep the oxygen cycle stable? a. cutting down jungles to create farmland b. eliminating parks in large cities c. dumping toxic chemicals into the ocean d. reducing the amount of deforestation d. reducing the amount of deforestation