Question

Every time a child visited a cousin who has two

Answer 1

(1) normally harmless cat antigens stimulated
the immune system

Answer 2

Answer:

(1) normally harmless cat antigens stimulated

the immune system

Explanation:

It isn't the fault of the respiratory system that the antigens produces an immune response to cat antigens but the specific genotype of the child. The genotype has developed his immune system too much sensitive mostly due to an anomaly or mutation. Now, normally harmless antigen will produce a immune response because it has enough potential of activation for induction of an immune response.