Final answer:
Alpha waves become more frequent and intense during meditation, reflecting a state of relaxation very similar to the early part of Non-REM stage 1 sleep.
Step-by-step explanation:
The type of brain waves that become more frequent and intense with meditation are c) Alpha waves. Alpha waves are a type of brain wave that occur during the early part of Non-REM stage 1 sleep, which is a transitional phase between wakefulness and sleep.
These waves are characterized by a frequency of 8-12 Hz and are associated with a state of relaxation that is not quite sleeping but is also not fully awake. As a person meditates, they increase their alpha brain wave activity, which reflects a relaxed state of mind.