8. Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

i) The air tubes of insects

(ii) Skeletal structures surrounding the chest cavity

(iii) Muscular floor of the chest cavity

(iv) Tiny pores on the surface of the leaf

(v) Small openings on the sides of the body of an insect

(vi) The respiratory organs of human beings

(vii) The openings through which we inhale

(viii) An anaerobic organism

(ix) An organism with a tracheal system 

9. The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km, there is no air. 

(b) The amount of air available to a person is less than that available on the ground.

(c) The temperature of the air is higher than that on the ground.

(d) The pressure of air is higher than that on the ground.