What are three things scientist must do for their experiment to be scientific

The finches on the galapagos island were similar in form except for variations of their beaks. darwin observed that these variations were useful for: attracting a mate defending territory building nests gathering food

Which line in the graph above best illustrates an effect of the carbon dioxide level in the blood on breathing rate before, during and after a period of exercise? 1.b,2.c,3.a,4.d

An uncomfortable feeling in the ears when descending in an airplane is caused by changes in air pressure on the: a. inner ear b. middle ear c. eardrum d. hammer/anvil