SCUBA-DIVING BECAME A _____ SPORT AFTER THE INVENTION OF SPECIAL BR...

6. - DE KIEM TRA HOC KI 2 LICH SU
DE KIEM TRA HOC KI 2 LICH SU

6. Scuba-diving became a _____ sport after the invention of special breathing equipment.

A. popular B. healthy C. boring D. free