The endosymbiotic theory says that precursor eukaryotic cells acquired cilia by endosymbiosis with a(n) ancestor and others gained photosynthetic ability from endosymbiosis with a(n) ancestor.

The correct answer is spirochete and cyanobacteria

Explanation:

The endosymbiotic theory states that the eukaryotic cells are evolved from prokaryotic cells when a larger prokaryotic cell engulfed the smaller prokaryotic cell. The presence of chloroplast and mitochondria supports this theory.

After genetic analysis of chloroplast DNA, it was seen that it closely resembles the cyanobacterial DNA which shows that ancestor host cell gained photosynthetic ability from endosymbiosis with a cyanobacterial ancestor.  

It was also seen that ancestral host cells engulfed spiral bacteria called spirochetes which helped them to produce cilia for example tail on sperms is the result of endosymbiosis of spirochete. So the right answer is spirochete and cyanobacteria.

the answer is c on e2020, bud.