If a test measures what it is supposed to measure, we say that it is ______

Research using harmless infrared light to study which parts of a stimulus an infant scans,

indicates that one-month-old infants a. gaze at the edges of the stimulus. b. shift their gaze between the center and borders of the stimulus. c. scan the interior of a stimulus. d. scan the stimulus in a circular pattern. e. perceive objects as wholes.

Vaccination is often an effective preventive measure because

A) viruses have a memory. B) the adaptive immune system has a memory. C) conspecifics have a memory. D) the innate immune system has a memory. E) the acquired immune system has a memory.