Answer :

The term that means a communication connection can send or receive data at one time is "Half-duplex."

Half-duplex communication allows data transmission in both directions, but not simultaneously. It means that the connection can either send or receive data at any given time, but not both at once. This is different from full-duplex communication where data can be sent and received simultaneously.

In contrast:
- TCP/IP is a set of protocols used for internet communication, it does not specifically refer to the simultaneous sending and receiving of data.
- Ethernet is a common type of network technology, but it doesn't specifically indicate the ability to send or receive data at one time.
- Time critical refers to tasks or processes that require immediate attention due to strict timing constraints, but it does not relate to the simultaneous data transmission capability of a communication connection.