20. State the first stage of soil formation from rocks.

21. Why is it important to look left, right then left again before crossing the road?

22. What is the importance of human teeth in the digestion of food?

23. What type of electricity is obtained by rubbing a plastic material against hair woollen cloth?

24. Apart from contour ploughing, strip cropping and mulching, give one other practice which is useful for soil conservation on a hilly ground.

25. What happens to the blood as it passes through the kidney?

26. What type of change occurs to an egg which has been left in boiling water for more than ten minutes?

Use the diagram of a leaf below to answer questions 277 and 28.

27. What is the part marked P?

28. Give one of the functions of part E.

29. Why do you think photosynthesis is not likely to take place at night?

30. State any one physical change which occurs in female adolescents but does not occur in the male ones.

31. Why is it dangerous to stay near someone who is smoking?

32. Why is osmosis an important process for plants?

33. What is the danger of taking drugs which are not prescribed by a health worker?

34. Give one example in which the filtration process is used at home.

35. When Peter looked into the plane mirror, he saw his face at the back of the mirror. How did his face get into the back of the mirror?

36. Why is it advisable for parents to take their children for immunisation?

37. Why should girls avoid teenage pregnancy?

38. How can water vapour be turned into liquid?

39. Why is it not advisable t use water to put off fire caused by petrol?

40. What is the importance of keeping clothes clean?