Explanation:
Broadband communication refers to high-speed transmission of data over a wide range of frequencies. It allows for the simultaneous transmission of multiple signals and enables faster and more efficient communication. There are several mediums used for broadband communication, but one of them is not considered a broadband communication medium. Let's analyze each option to determine which one is not a broadband communication medium.

Microwave:
Microwave communication involves the use of high-frequency radio waves to transmit data. It is commonly used for point-to-point communication over short to medium distances. Microwaves can transmit large amounts of data and are often used for wireless broadband connections.

Fibre optic cable:
Fibre optic cable is a medium that uses thin strands of glass or plastic to transmit data using light signals. It offers high data transfer rates, low latency, and is capable of transmitting large amounts of data over long distances. Fibre optic cable is widely used for broadband internet connections.

Twisted pair:
Twisted pair refers to a type of cable that consists of two insulated copper wires twisted together. It is commonly used for telephone and Ethernet connections. While twisted pair cables can transmit data, they are not typically used for broadband communication due to their lower data transfer rates and limited bandwidth.

Coaxial cable:
Coaxial cable consists of a central conductor surrounded by an insulating layer, a metallic shield, and an outer insulating layer. It is commonly used for cable television and broadband internet connections. Coaxial cables offer high bandwidth and can transmit large amounts of data over long distances.

Conclusion:
Based on the analysis of the options, it can be concluded that twisted pair cable is not a broadband communication medium. While it can transmit data, it is not typically used for broadband communication due to its lower data transfer rates and limited bandwidth.