Which observation proves that a cell is a eukaryote?
a. the cell has a cell membrane.
b. the cell contains a nucleus.
c. the cell uses ribosomes to create protein.
d. the cell contains dna

Which conditions are necessary for natural selection to occur? select all of the answers that apply. a. inheritable adaptations vary among individuals. b. the population size is increasing. c. more individuals are born than can survive. d. fitness varies among individuals. e. the environment changes suddenly and drastically.

Which of the following sex and generation combinations directly produces the pollen tube of angiosperms? a) male gametophyteb) female gametophytec) male sporophyted) female sporophyte

Select the correct answer from each drop-down menu. in an experiment, dr. travis examined the effects of calcium intake on osteoporosis, a condition that causes an increased risk of bone fractures. the amount of calcium is variable. the risk of bone fractures .