Which character is often used to identify registered trademarks and is available on the Insert tab and Symbols group?

trademark symbol (™)

Explanation:

The Trademark Symbol is represented by the capital letters "TM" (TM), which means Trade Mark.

Alt code for symbol "tm"

Press Alt and, keeping it, type a code on the numeric keypad. If you are on a laptop, read Alt Code symbols on Laptop keyboard.

Th small little T in a circle