Efficiency is a measure of how much of the work put into a machine is converted into useful output work. Why can efficiency never reach 100%? А) acceleration
B) elasticity
C)friction
D) gravity

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.

What do scientists need to look at before developing an argument

Ascientist wants to determine the effect of a new type of gasoline. he fillsone car with normal gasoline and another identical car with the new gasoline.which is the control group? a. the new type of gasolineb. the car with the normal gasolinec. the car with the new gasolinethe amount of gasoline usedd. the amount of gasoline used