Using eegs, researchers try to identify while subjects are engaged in different tasks. a. brain patterns b. mental capabilities c. electrical activity d. brain waves

A. brain patterns

Explanation:

EEG's meaning electroencephalography is a procedure use to measure brain waves and test electrical signal of the brain . The procedure is use by doctors  to diagnose sleep disorder and epilepsy.  It gives information on the cognitive , emotional and behavioral condition of an individual.

The subject might be engaged in different tasks like creativity and imaginative task, the electroencephalography measures the brain pattern.

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

10 years is the answer