Which statement best describes the limits of science? a. science cannot answer difficult questions. b. science can answer only mathematical questions. c. science cannot answer philosophical questions. d. science can answer all questions.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Which symbols below represent the ions found in the glass of water ? a. oh- and h+ b. co2 and o2 c. o2 and h2 d. nh3- and h+

When a gasoline engine burns gasoline, what type of chemical reaction is occurring?