16. The most important force that provides resistance to particles towards entertainment is

A. frictional resistance
B. particle cohesive bonds
C. particle adhesive bonds
D. momentum

17. The metamorphism which involves the chemical replacement of elements in rock minerals when gases and liquids permute into bedrock is called

A. metasomatic metamorphism
B. dynamic metamorphism
C. thermal metamorphism
D. contact metamorphism

18. The magnetosphere becomes unstable during the magnetic storms during a period of

A. initial phase
B. storm sudden commencement phase
C. main phase
D. None of the above

19. The major cause of species extinction is

A. agricultural activities
B. extraction (including mining, fishing, logging)
C. development (human settlements, industry)
D. habitat loss and degradation

20. The major crops found in Sudan are

A. rice, barley, bananas, cocoa
B. maize, cotton, bananas, groundnut
C. bajra, oats, tobacco
D. wool, wine, jute