Here are the best options for each numbered blank in the passage:

23. **C. safe**
24. **A. who**
25. **B. update**
26. **C. about**
27. **D. playing**

So the completed passage would read as follows:

"When you game online, be careful when you make friends with strangers. What should you do? Firstly, remember that it is **safe** to lie online and some of these “online friends” may be adults **who** want to harm you. Secondly, never give your personal information such as your full name or your hometown. Thirdly, only play online games when you have **updated** antivirus software. In addition, tell your parents what games you are playing and what you love **about** them. In short, just like in the real world, you need to be careful **playing** with strangers."