The correct answer is $\boxed{\text{B}}$.
The sacrificing ratio is the ratio in which the old partners give up their share of the profit to the new partner. It is calculated by subtracting the new partner’s share from the old partners’ original share.
In this case, the new partner’s share is 1, so the sacrificing ratio is $4 – 1 = 3$ for A, $3 – 1 = 2$ for B, and $2 – 1 = 1$ for C. Therefore, the old partners’ sacrificing ratio is $3 : 2 : 1$.
Option A is incorrect because the old partners’ sacrificing ratio is not equal.
Option C is incorrect because the old partners’ sacrificing ratio is not $3 : 2 : 1$.
Option D is incorrect because the old partners’ sacrificing ratio is not $5 : 3 : 2$.