Answer: D. They turn red litmus paper blue and taste bitter.
Explanation:
Acids are those substances which either donates hydrogen ions when dissolved in water. They have pH ranging from 1 to 6.9. They are sour in taste. They dissolve metals to give hydrogen gas. They turn blue litmus red.
Bases are those substances which either donates hydroxide ions when dissolved in water or donates a pair of electrons. They have pH ranging from 7.1 to 14. They are bitter in taste. They are slippery in nature. They turn red litmus blue.