Final answer:
RG-59 is the correct answer for terminating a coaxial cable, as it is a type of coaxial cable. RJ45, DB9, and RS-232 are incorrect because they are not used for terminating coaxial cables.
Step-by-step explanation:
The item used to terminate a coaxial cable among the options provided is RG-59. The RG-59 is a type of coaxial cable often used in residential environments for video and broadcasting, especially for cable TV systems. Other connectors, such as an RJ45 or a DB9, are not used to terminate a coaxial cable. RJ45 is typically used for Ethernet networking to connect computers and other devices to a network. DB9 (or DE-9), on the other hand, is a serial port connector found on some types of computer hardware. Finally, RS-232 is not a cable or connector type but rather a standard for serial communication typically used in computer serial ports.