Final answer:
Lemon juice is acidic, evident from its sour taste and the fact that it turns blue litmus paper red, both of which are hallmark properties of acids.
Step-by-step explanation:
Lemon juice has a sour taste and turns litmus to red. Based on the properties shared, lemon juice is acidic (option 2). Acids are known for their sour taste, which is a key characteristic of substances like lemons, vinegar, and sour candies. Additionally, acids change the color of acid-base indicators such as litmus; more specifically, they turn blue litmus paper red. Furthermore, it is a well-established fact that acids react with active metals to yield hydrogen gas.
This reactivity is often categorized in an activity series, where metals more reactive than hydrogen can displace hydrogen from acids in a single-replacement reaction. From the given description, it is evident that lemon juice exhibits typical acidic properties and is neither neutral (option 1), caustic (option 3), nor basic (option 4).