Question

which of the following is an example of an adaptation?
microbial resistance to an antibiotic
plants positioning their leaves to maximize sunlight absorption
ears popping in the water after cliff diving into the ocean
an amoebas contractile vacuole expelling excess water

Explanation:

Adaptation refers to a trait that helps an organism survive and reproduce in its environment. Plants positioning their leaves to maximize sunlight absorption is an adaptation as it aids in photosynthesis (a key survival and growth process). An amoeba's contractile vacuole expelling excess water is a cellular mechanism (osmoregulation) but not a trait adaptation in the evolutionary sense for the whole organism. Ears popping is a physiological response (pressure equalization) not an adaptation. Microbial resistance to an antibiotic is a genetic change (mutation) leading to resistance but it's a response to selective pressure (antibiotic use) rather than a trait developed for survival in the natural environment in the traditional adaptation sense (like a physical or behavioral trait for the organism's benefit in its habitat).

Answer:

Plants positioning their leaves to maximize sunlight absorption.