The enamel of the teeth is made of a compound 'X'. It is the hardest substance of the body. It does not dissolve in water but gets corroded when the pH of mouth is lowered below 5.5 (a) Identify the compound 'X' (b) How does it undergo damage due to eating sweets? What should we do to prevent tooth decay?

What type of questions asked from the lesson of magnetic effect of electric current 

Wavelength of green light is

A) 400-450 nm

B) 500-550 nm

C) 660-720 nm

D) 720-800 nm

What is the difference between anaerobic & aerobic respiration? Name some organism that uses the aerobic mode of respiration?

What are the main components of our environment? Explain each of them briefly.

What are examples of hydrotropism plants?