Every time a child visited a cousin who has two
cats, the child’s eyes turned red, itched, and
began to water. Then, the child began to have
trouble breathing. It is most likely that the child
reacted this way because
(1) normally harmless cat antigens stimulated
the immune system
(2) it is difficult for the respiratory system to
filter cat antigens out of the inhaled air
(3) cat antigens are a health hazard, since they
always cause disease
(4) cat antigens stop the immune system from
making antibodies, so bacteria cause these
responses