Tasting or touching solutions to identify whether it is an acid or a base is something that you should always avoid since it can be dangerous and, in some cases, deadly.
Phenolphthalein is typically used to test the pH level of a solution. Since you can determine whether a solution is an acid or a base by identifying the pH level, this is one of the correct answers.
However, the question says to "select all that apply," so let's also check the last option, litmus paper.
Litmus paper is commonly used to identify whether something is an acid or a base. When blue litmus paper is exposed to an acid, it turns red. When red litmus paper is exposed to bases, it turns blue.
This means that the answers you should select are both litmus paper and phenolphthalein.
Hope this helps!
