What ability did early eukaryotic cells have to survive without?

Question

A. the ability to engulf other cells

B. the ability to undergo mitosis

C. anaerobic fermentation

D. electron transport

E. the ability to shift internal structures

Answer 1

D.

The theory is that at some point, early eukaryotic cells engulfed bacteria, but the bacteria survived and evolved to become mitochondria.  

(beware:  that's a very simplified account of a complex idea!)