Question

How is the oxygen cycle effected? 

1. Human activities 

2. Running of automobiles 

3. Consumption of fossil fuels 

Choose the correct code 

(a) 1 and 2 (b) 2 and 3 (c) 1 and 3 (d) 1, 2, 3

Answer 1

(d) The oxygen concentration in atmosphere is 21%. The oxygen cycle is effected by human activities such as running automobiles and consumption of fossil fuels which release more carbon dioxide in the atmosphere.