a. vinegar
b. Mineral deficiencies in the body can make joint pain worse. Because Vinegar contains the calcium, magnesium, potassium, and phosphorus your body needs, it helps as a supplement and therefore reduces pain.
1. in making fertilisers which are chemical compounds or salts to increase fertility of soil.
2. lithium hydroxide is used in space because of its high absorption of carbon dioxide and the small amount of heat produce by the reaction.
3. Acid rain has a lower pH than "normal" rain . Rain is naturally somewhat acidic with a pH between 5.0-5.5 typically. Acid rain has a pH that is below this: 4.4-4.2
4. lemon juice is an anti bacterial and a good germicidal solution which helps in removing the unseen bacteria on our hands.
Hope this helps :)