Available Answers

1. 1.

   Choose the correct option.

   1. Changes in the structure or behaviour of an organism that help it to survive in a particular habitat are called
      1. camouflage
      2. habitat
      3. acclimatization
      4. adaptation
   2. A fixed quantity with respect to which a physical quantity is measured is called
      1. measurement
      2. estimation
      3. ruler
      4. unit
   3. Which of these help in vermicomposting?
      1. insects
      2. earthworms
      3. fungi
      4. none of these
   4. Light always travels in a 
      1. straight path
      2. curved path
      3. zig zag path
      4. all of these
   5. Tap roots are also called
      1. fibrous roots
      2. true roots
      3. shrubs
      4. herbs
   6. Water that is suitable for drinking is called
      1. polluted water
      2. portable water
      3. salt water
      4. both (a) and (c)
   7. Which of these gases is needed for respiration?
      1. Carbon dioxide
      2. Nitrogen
      3. Oxygen
      4. All of these
   8. Nitrogen constitutes about ______ per cent of air.
      1. 1%
      2. 21%
      3. 0.03%
      4. 78%
   9. This device is used to open and close an electric circuit.
      1. Electric torch
      2. Electric switch
      3. Fuse
      4. None of these
   10. A circuit through which current cannot flow is known as
       1. closed circuit
       2. short circuit
       3. open circuit
       4. electric circuit
   S A M P L E

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   Answer:

   S A M P L E

   1. (d) adaptation
   2. (d) unit
   3. (b) earthworms
   4. (a) straight path
   5. (b) tru
   6. (b) portabl...
   7. ...
   8. ...
   9. ...
   10. ...
2. 2.

   Write one word for the following.

   1. An object that attracts objects made of iron
   2. Any object that is a source of light
   3. Special structure that can be filled with air or emptied to help fish move up and down in water
   4. A very convenient source of electric current
   5. Something that can be built on rivers to control drought and flood
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   Answer:

   S A M P L E

   1. Magnet
   2. Luminous object
   3. Swim bladder
   4. Battery
   5. Dam
3. 3.

   Circle the odd one.

   1. Lamp	Candle	Sun	(Hint: It is not an artificial source of light.)
   2. Iron	Wood	Plastic	(Hint: It is a magnetic object.)
   3. Melting of ice	Evaporation of water	Ripening of fruits	(Hint: It is not a reversible change.)
   4. Eraser	Pan	Pencil	(Hint: This object is a conductor of heat.)
   5. Cubit	Ruler	Fathom	(Hint: This is not an ancient method of measurement.)

    

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   Answer:

   S A M P L E

   1. Sun: It is a natural source of light, unlike lamp and candle...
   2. Wood: It is not magnetic, unlike iron and plastic...
   3. Ripening of fruits: It is an i...
   4. ...
   5. ...
4. 4.

   Why it is not advisable to sieve wheat flour? How should wheat flour be cleaned instead?

5. 5.

   Name the instrument that helps us to find the directions. How does it work?

6. 6.

   How is a pinhole camera made?