The monroe doctrine (1823) could have been used in response to which of these events?
a) the french invasion of mexico by napoleon iii
b) the secession of south carolina from the union
c) the removal of indian cultures from the american west
d) the war with mexico for control of the american southwest

D). This led to his first patent and a sizable financial reward while still in high school.

Explanation:

As per the question, the last option displays a fact instead of an opinion as it involves the description of an information('first patent and a sizable financial reward') that is compatible with the objective reality and possesses the ability to be verified or proved as true using evidences. The information about 'first patent or the financial award' could be verified to be true by using the past records of Dean Kamen's achievements as evidence. Thus, option D is the correct answer.