What's a fossil that's formed when an outline of the original organism is formed from left-over carbon?

Which of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

Match the types of competition to their descriptions

What are the two causes of density in deep current waters? a. salinity (how much salt) of the water and high temperaturesb. salinity (how much salt) of the water and low temperatures c. oxygen content of the water and high temperatures. d. oxygen content of the water and low temperatures