Concept:An atomic orbital is a quantum mechanical region around the nucleus where the probability of finding an electron is highest.Explanation:In the Bohr model, electrons were thought to move in fixed circular paths. However, quantum mechanics shows that electrons do not travel in definite circular orbits. Instead, an orbital is a three-dimensional space around the nucleus where an electron is most likely to be found. Electrons behave as clouds of probability rather than particles moving along fixed paths. Therefore, the description in option A, C, or D is incorrect because they all refer to a definite "path" of motion. The correct definition is the region of highest probability of locating an electron.Answer:B. A region around the nucleus where electrons are most likely to be found.