Which of the following is the hardest substance?
Which of the following is the hardest substance?
		A. Copper
B. Diamond
C. Iron
D. Silicon
		A. Copper
B. Diamond
C. Iron
D. Silicon
		A. 7
B. 13
C. 27
D. 62
		A. Duralumin
B. Y-Alloy
C. Alnico
D. Aluminium bronze
		A. Power
B. Electric Current
C. Energy
D. Time
E. None of these
		A. 55 million
B. 66 million
C. 75 million
D. 85 million
The ozone layer is at height of________kilometers from the surface of the Earth?
A. 10 to 20
B. 20 to 30
C. 30 to 40
D. 40 to 50