For the reaction between gaseous chlorine and nitrogen monoxide: 2NO + Cl2 = 2NOCl?

Doubling the concentration of chlorine doubles the rate, so its first order in chlorine. Doubling both nitrous oxide and chlorine octuples the rate. Doubling the chlorine itself doubled the rate, so doubling the nitrous oxide quadruples the rate. The reaction then is second order in nitrous oxide. therefore A is the correct answer.