Critical Reasoning

In the first decade following the founding of the British Labour party, the number of people regularly voting for Labour increased fivefold. The number of committed Labour voters increased a further fivefold during the party's second decade. Since the increase was thus the same in the first as in the second decade, the often-made claim that the Labour party gained move voters in the party's second decade than in its first is clearly false.
The reasoning in the argument is flawed because the argument
(A) fails to specify dates necessary to evaluate the truth of the conclusion, even though the argument depends on distinguishing between two time periods
(B) draws a conclusion that cannot be true if all the data advanced in its support are true
(C) relies on statistical evidence that, strictly speaking, is irrelevant to establishing the conclusion drawn
(D) fails to allow for the possibility that the policy positions advocated by the Labour party changed during the period in question
(E) overlooks the possibility that more elections were held in one of the two decades than were held in the other

Should be B.
Whats the OA?

IMO B

Stumped

# of labor voters before launch of BLP: x
# of labor voters in the 1st decade of launch: 5x
# of labor voters in the 2nd decade of launch: 25x


=> the # of voters gained in the 2nd decade (20x) is more than the # of voters gained in the 1st decade (4x)
=>the claim cannot be false

hence, B

I am leaning more towards B, but I'm not sure about it.