____________ is the percentage of nitrogen in air.

(a)

78%

(b)

21%

(c)

0.03%

(d)

1%

Gas exchange takes place in plants using __________

(a)

Stomata

(b)

Chlorophyll

(c)

Leaves

(d)

Flowers

The constituent of air that supports combustion is _________________

(a)

Nitrogen

(b)

carbon-di-oxide

(c)

Oxygen

(d)

water vapour

Nitrogen is used in the food packaging industry because it ________________

(a)

provides colour to the food

(b)

provides oxygen to the food

(c)

adds proteins and minerals to the food

(d)

keeps the food fresh

_______ and _________ are the two gases, which when taken together, make up about 99 percentage of air.
I. Nitrogen
II. Carbon-di-oxide
III. Noble gases
IV. Oxygen

(a)

I and II

(b)

I and III

(c)

II and IV

(d)

I and IV