Answer:
A. Fact
Explanation:
This is a specific data point, the "for violence' is just additional information, but there is no personal opinion in this statement.
You wouldn't want to swim in the Amazon when PIRANHAS are around. <span />
"Thus the small differences distinguishing varieties of the same species, steadily tend to increase, till they equal the greater differences between species of the same genus, or even of distinct genera."
<em>Genera</em> is plural for genus.
<em>Genus</em> means biological classification of things that have common characteristics and can be divided into subcategories.
Therefore, the correct answer is "same/similar family common characteristics."