In the context of the technologies developed to improve the efficiency and quality of digital communications, $\_\_\_\_$ divide$($s$)$ each channel into six time slots.

a$.$ Code Division Multiple Access $($CDMA$)$

b$.$ Time Division Multiple Access $($TDMA$)$

c$.$ Transmission Control Protocol $($TCP$)$

d$.$ Mobile Telephone Switching Offices $($MTSOs$)$