20. which of the following improves the efficiency of a machine?
cal. reducing friction
b. adding more energy
c. running it faster
increasing friction

Out of the seven main animal groups (fish, mammals, birds, insects, reptiles, amphibians, and arachnids), how many contain members with internal backbones? a. 5 b. 3 c. 7 d. 1

Whay is the following best defines climate

Glycogen is an energy-storage molecule in humans. a hormone that is called insulin controls the storage of glycogen in the liver. insulin is made up of amino acids.