(A) is necessary, because if it were not true — if Doctrine 1 allows noneconomic factors in explanations of historical events — then the author’s premise wouldn’t show that Doctrine 1 is wrong. The author mistakenly believes that Doctrine 1 doesn’t allow for noneconomic factors; this is why he thinks pointing out some events involve both economic and non-economic factors goes against Doctrine 1.

The author doesn’t have to believe Doctrine 2 places importance only on childhood experiences. Doctrine 2 may focus on early childhood experiences, but there’s no indication the author thinks no other psychological experiences are relevant to Doctrine 2.

The author simply points out that some events involve both factors. But one kind of factor can be more influential than the other; that wouldn’t undermine the author’s line of reasoning. To the author, as long as an event involves both factors — regardless of whether they are equally influential or not — that shows both doctrines are wrong.

The author simply points out that there are some events that involve both factors. But the author doesn’t assume that both kinds of explanations are likely to have been proposed for “any” historical event.

The author simply points out that there are some events that involve both factors. But the author doesn’t assume that both factors are necessary to understand “any” historical event.