Concept:A base turns red litmus paper blue, while acids and neutral substances do not change its colour.
Explanation:Red litmus paper is an indicator used to test whether a solution is acidic or basic.
If the solution is basic, red litmus paper changes to blue.
In solution A, red litmus paper changed colour to blue.
This shows that solution A contains a basic substance.
Car battery fluid and orange juice are acidic, so they cannot turn red litmus blue.
Salt solution is neutral and also leaves red litmus paper unchanged.
Baking soda is a mild base, so it turns red litmus paper blue.
Hence, the content of solution A is likely baking soda.
Answer:C. Baking soda