An impairment or combination of impairments that significantly limits one’s physical or mental ability to do basic work activities, the abilities and aptitudes necessary to do most jobs. Examples of basic work activities include: walking, standing, sitting, lifting, pushing, pulling, reaching, carrying, and handling; seeing, hearing, and speaking; understanding, carrying out, and remembering simple instructions; use of judgment; responding appropriately to supervision, co-workers, and usual work situations; and dealing with changes in a routine work setting.