It's OVER! Thank you so much, J.Y.! I wouldn't have done it without you and those wonderful tutorials. Three cheers for 7sage!

JY: Why do you infer that DLS is the same as a Driver with a higher number of demerit points? Symbolically, why do you infer that Driver+ Large # of Demerit Points+ Serious offense = D+L (as stated in the last conditional statement in the stimulus)?

Try to think of endosymb as what happens when a Y cell engulfs an X cell. The Y cell eats the X cell, thereby taking in the X-cell nucleus. The Y nucleus blends with the X nucleus in the Y cell ( via endosymb) to produce the resulting nucleomorph (i.e., a Y-X nucleus). If that nucleomorph is found within the Chlor-plant, then it follows that the Chlor-plant's cells are Y-X cells (because how else are you going to get a nucleumorph/Y-X nucleus). If that's the case, then the plant must have originated from two cells having combined via endosymb.

Keep in mind that the nucleomorph is not the parent cell -- it's the newly combined nucleus as a result of two host cells (Y and X) combining. Who/what exactly was the parent cell is irrelevant here (we don't need to know what the Y or X cells were). All we know is that those parent cells joined together and created a nucleomorph.

I gave it my best shot. Hope this helps...