Court records from medieval France show that in the years 1300 to 1400

This question is about statistic in Critical Reasoning. Very common and classical in CR, you will see this kind of question over and over again in real tests. In reality, you see this type of CR mostly in newspaper, magazines or even in statistic researches.

The form of this question is:
X appears more often than Y
Conclusion: X is more important/serious/dangerous/… than Y

IMPORTANT Assumption: X and Y cover the SAME scope. If that is NOT the case, the comparison is invalid.

APPLY TO THE QUESTION.
Fact: Court records from medieval France show that in the years 1300 to 1400 the number of people arrested in the French realm for "violent interpersonal crimes" (not committed in wars) increased by 30 percent over the number of people arrested for such crimes in the years 1200 to 1300.
Fact: The increase was not the result of false arrests;
Conclusion: medieval France had a higher level of documented interpersonal violence in the years 1300 to 1400 than in the years 1200 to 1300.

Assumption: Court records in 1300-1400 and those in 1200-1300 covered the SAME scope.

Which one of the following statements, if true, most seriously weakens the argument?

ANALYZE EACH ANSWER:

(A) In the years 1300 to 1400 the French government's category of violent crimes included an increasing variety of interpersonal crimes that are actually nonviolent.
Correct. A undermines the conclusion by showing that records in 1300-1400 covered a more broaden range than those in 1200-1300. Thus, the comparison of the argument is INVALID.

(B) Historical accounts by monastic chroniclers in the years 1300 to 1400 are filled with descriptions of violent attacks committed by people living in the French realm
Wrong. Irrelevant. Just the description of violent attacks does not help anything.

(C) The number of individual agreements between two people in which they swore oaths not to attack each other increased substantially after 1300.
Wrong. Irrelevant. Nothing about the agreement between two people.

(D) When English armies tried to conquer parts of France in the mid- to late 1300s. violence in the northern province of Normandy and the south-western province of Gascony increased.
Wrong. Does not weaken the conclusion. In fact, D may show that the comparison in the argument is valid.

(E) The population of medical France increased substantially during the first five decades of the 1300s until the deadly bubonic plague decimated the population of France after 1348.
Wrong. Irrelevant. Nothing about the deadly plague.

Hope it helps.