Final answer:
Considering the low risk per rem for heritable effects and fatal cancers, the answer to the question regarding the number of such events per year from 2-3 million x-rays is 'A few hundred; a few dozen.'
Step-by-step explanation:
The question asks about the number of heritable effects and fatal cancers induced per year by 2-3 million x-rays. If the risk of a radiation-induced hereditable effect is about 100 in a million for each rem, and the overall risk of a radiation-induced cancer death per year per rem is about 10 in a million, considering the quantity of x-rays, the likelihood would be in the lower end of the spectrum. Thus, the correct answer can be inferred to be B. A few hundred; a few dozen. This is because for millions of x-rays, only a few would induce heritable effects or fatal cancers, given the low risk per rem as provided by the lifetime exposure data.