Salts are formed when an ionic bond is formed between two elements in the compound. Let us recall that the kind of bond formed between any two elements depends on the magnitude of electronegativity difference between the two elements.
Among the options listed, the highest degree of electronegativity difference occurs for the bond between Cs and I. This implies that this bond is ionic and the combination of the two elements will lead to salt formation.
decrease in temperature , decreases the kinetic movements of the gase molecules as a result decreases the frequency of collisions between gas molecules A and B consequently decreases the rate of reactions of gases A and B
