Pleas explain this question

Pleas explain this question What is meant by potable water? SECTION B 2 21. Suggest a suitable word for each of the following statements- Chemicals added to food to prevent growth of micro-organisms. b) Nitrogen fixing bacteria present in the root nodUleS Of legumes. c) Agent that spreads pathogens from one place to another. Write three uses of metals and three uses of non metals. Classify the following terms into cells, tissues and organs in a tabular form. Heart. . Brain, hand

Dear Student,

Q 21
(a)Peservatives
These chemicals preserve the food from decaying, hence they are called preservatives.
(b)Rhizobium
Multiple interactions between the roots and the leguminous plants leads to nodule formation
(c) Vectors
Agents like mosquitoes, rats etc. spread pathogens from one place to another hence causing illnesses like Malaria, Plague etc.
Q 22
Three uses of metals are: 
1. Metals are ductile and can be drawn into wires so copper is used for electric wires.
2. Metals are malleable and and can be drawn into sheets and are thus used in making many metal objects like metal cases.
3. Metals are good conductors of heat and so are used in cooking utensils.
The three uses of non metals are :
1. Non metals are used in making many synthetic products .
2.Chlorine is used in bleaching.
3.Wood is used for burning.

For remaining queries we request you to post them in separate threads to have rapid assistance from our experts.

Regards