Given that Solution A has a pH of 13, and Solution B has a pH of 4, we know two important facts to answer this question according to the pH scale.
The pH scale ranges from 0 to 14, with 7 being neutral.
If a substance has a pH less than 7, it is considered acidic.
If a substance has a pH greater than 7, it is considered basic, or alkaline.
If a substance has a pH of 7, it is considered neutral.
Let's apply these facts to our solutions.
Solution A has a pH of 13. Comparing this to the pH scale, we see that 13 is greater than 7. According to our scale, this means that Solution A is basic.
Solution B has a pH of 4. Comparing this to the pH scale, we see that 4 is less than 7. According to our scale, this means that Solution B is acidic.
So, after comparing Solutions A and B to the pH scale, we can conclude that Solution A is basic and Solution B is acidic.