A student was given four unknown solutions in test-tubes marked A, B, C and D and asked to test them with universal indicator solution. He observed that on putting universal indicator solution, the solutions A, B, C and D turned blue, orange, green and red respectively. The test-tube which contains sodium chloride solution is :
(1) A
(2) B
(3) C
(4) D

Correct answer: (3) C

Explanation:  NaCl is formed by the reaction of strong acid and strong base therefore, it is neutral and will show green colour with a universal indicator.