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Common mistakes and misconceptions
Natural selection is a mechanism, or cause, of evolution. Adaptations are physical or behavioral traits that make an organism better suited to its environment. Heritable variation comes from random mutations. Random mutations are the initial cause of new heritable traits.
Answer:
The second one is correct
Explanation:
A leukocyte is responsible for the immune system
Answer: (c) skeleton
Explanation: The musculoskeletal system is made up of the body's bones (the skeleton), muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together.