What are the effects of human activity?

What do your cells need to live? a. carbon dioxide b. carbon c. air d. oxygen

Which of the following statements best distinguishes a hypothesis from a theory? a. theories are hypotheses that have been proved. b.hypotheses are guesses; theories are correct answers c. hypotheses usually are relatively narrow in scope; theories have broad explanatory power. d. theories are proved to be true; hypotheses are often contradicted by experimental results.

Omar paddles a canoe downstream at a rate of 5 mi/hr. the stream is flowing at a rate of 12 mi/hr. what is the actual velocity of the canoe? a: 5 mi/hr, downstream b: 7 mi/hr, downstream c: 12 mi/hr, downstream d: 17 mi/hr, downstream