How to choose the content of your reply in the PC version of Steins;Gate

Under normal circumstances, press the "P" key on the keyboard to pop up the phone on the right side of the screen. There is a box in the upper left corner of the screen showing the date. Sometimes it will show that someone has sent you a message. , and then press the P key, you will be asked to open the text message. Sometimes there are blue fonts in the text message, which are options and the topic you choose to reply to.