Red litmus turns blue in which type of solution?

Correct answer: Basic solution

Red litmus turns blue in a basic or alkaline solution because the indicator responds to the hydroxide-rich chemical environment. This colour change is a standard qualitative test for bases. An acidic solution turns blue litmus red, while a neutral solution normally produces no change. A pure sugar solution is generally treated as neutral and therefore does not turn red litmus blue. Thus option B correctly identifies the solution type.