Which equation below has the fewest number of oxygen atoms?

Which equation below has the fewest number of oxygen atoms?

2AgNO3 + K2SO4 --> Ag2SO4 + 2KNO3

C2H4 + 3O2 --> 2CO2 + 2H2O

4Fe + 6H2O + 3O2 --> 4Fe(OH)3

6CO2 + 6 H2O --> C6H12O6 + 6O2

The equation that has the fewest number of oxygen atoms is:

2AgNO3 + K2SO4 --> Ag2SO4 + 2KNO3