The type of b cell which remains in the body after an invasion is over is called

memory cells

Explanation:

to fight the reoccurrence of the invasion

Sordoria is an haploid organism. As such, it is impossible to talk about chromosome arrangements with Sordoria as this phenomenon only occurs during meiosis and meiosis does not take place with haploid organisms.
I suggest a reformulation of the question. Sordoria is an organism that's highly used for genetics studies and the question might have a point if reformulated.