The six graphs in Figure 1.16 show frequently observed patterns of age-specific cancer incidence rates, in number of cases per 1000 people, as a function of age. The scales on the vertical axes are equal.

(a) For each of the six graphs, write a sentence explaining the effect of age on the cancer rate. 

(b) Which graph shows a relatively high incidence rate for children? Suggest a type of cancer that behaves this way. 

(c) Which graph shows a brief decrease in the incidence rate at around age 50? Suggest a type of cancer that might behave this way. 

(d) Which graph or graphs might represent a cancer that is caused by toxins which build up in the body over time? (For example, lung cancer.) Explain.

Figure 1.16

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(1) incidence 20 40 60 80 (III) incidence 20 40 60 80 (V) incidence 20 40 60 80 age age age (II) incidence 1 I 20 40 60 80 (IV) incidence 20 40 60 80 (VI) incidence 20 40 60 80 age age age