1. First, click on a text input box on the Apple phone. The Baidu input method keyboard will pop up below. Click on the "symbol" in the keyboard.

2. Then in the left list of "Symbols", select "Special" from the drop-down menu and click to enter.

3. After clicking, a list of special symbols will appear on the right side. Use your finger to drag down until you find the special symbol "?".

4. Finally, click the found symbol "?" to enter the trademark r in the text input box.