I received a strange message, only replied to a message, and didn't click the link. This mobile phone is infected with Trojan virus. How did you do that? You can get extra points

There are two possibilities: one is that the sender took advantage of the vulnerability of the Android SMS system, which led to secretly downloading and installing the Trojan after receiving or restoring this SMS, and the other is that the receiver did click on the link but was embarrassed to admit it. The latter is more likely.