Why do internodal segments of sugarcane fail to propagate vegatatively even when they are in contact with dump soil?

We use colours dissolved in water during Holi and clothes gets spoiled. Many colours used to celebrate Holi are oxidized metals or industrial dyes mixed with engine oil. Doctors say these are harmful colours which should be banned for usage. Manufactures mix dyes with colours, and sell them for their profits. Holi lovers can make their Holi colourful by using natural colours available in the market.Natural colours start fading when they come in contact with sun rays. (i) Why doctors say that synthetic colours are harmful? (ii) What are natural colours? (iii) As a student what initiative you will take to motivate your classmates to use natural colours in Holi? Give any suggestions.

Why do fresh grapes shrink, when they are soaked in a strong salt solution?

Why do fishes die when taken out of water?

Why does a car parked in sunlight remain hot from inside even when there is no sunlight ?

Name two metals that start floating after sometime when immersed in water and explain why they do so.

Why do the walls of the trachea not collapse when there is less air in it ?

Why do you feel lighter when you swim?

Why do we often sneeze when we inhale a lot of dust-laden air?