The term or protocol used for open wireless technology for data exchange over short distances is

Bluetooth is an open wireless technology for exchanging data between devices over short distances.

ISDN is a wired digital telephone service, not a short-range wireless link.

Wi-Fi is wireless too but is built for local-area networking over larger ranges than Bluetooth.

No other choice fits because Bluetooth is exactly the short-range wireless standard.

Bluetooth typically works within about ten metres and uses low power.

It is common for connecting headsets, keyboards and other nearby accessories.