People who are allergic to cats are actually allergic to certain proteins found in the animals' skin secretions and saliva; which particular proteins are responsible, however, varies from allergy sufferer to allergy sufferer. Since all cats shed skin and spread saliva around their environment, there is no such thing as a cat incapable of provoking allergic reactions, although it is common for a given cat to cause an allergic reaction in some -- but not all -- people who are allergic to cats. Which one of the following statements is most strongly supported by the information above? ['Not all cats are identical with respect to the proteins contained in their skin secretions and saliva.', 'The allergic reactions of some people who are allergic to cats are more intense than the allergic reactions of other allergy sufferers.', 'Any particular individual will be allergic to some breeds of cat but not to others.', 'No cat is capable of causing an allergic reaction in all types of allergy sufferers.']