This is a fairly common concept tested for O-level Chemistry and similar to these questions in my book 'Explain That! Chemistry (2nd Ed, 2020)'. Ammonia has a molecular mass of 17, hence is less dense than air. Air (average molecular mass is about 28.6) being denser, displaces ammonia out of the gas jar at the fastest rate (compared to A, nitrogen - molecular mass 28). Hence the answer is C. Oxygen (Mr 32) and S02 (Mr 64) are denser than air and hence will only diffuse out of the gas jar at a slow rate (recall the greater molecular mass of a gas, the slower the diffusion rate).