Which of the following gases are colorless but have specific odor?

I) O2→ Colorless  ; Cl2→colorless gasII) I2,Cl2 are gases −I2 Violet) ;Cl2 (Greenish Yellow) III) NH3→SO2; Colorless and NH3 has pungent small ; SO2 has suffocating odour IV) Colorless and odourless.