How does secondary endosymbiosis explain the origin of chlorarachniophytes?

Chlorarachniophytes acquired plastids from engulfing a green alga.

Chlorarachniophytes developed from the direct fusion of two prokaryotic cells.

Chlorarachniophytes originated through primary endosymbiosis with mitochondria.

Chlorarachniophytes acquired nuclei through secondary endosymbiosis.