Question

Bacteria that feed on dead or decaying material are: chemosynthetic photosynthetic saprophytic symbiotic

Answer 1

So, like most things in biology, either knowing the terms or knowing some Latin / Greek roots helps.
chemo- think chemicals
photo- light
sym- with

sapro- "rotten material"


as it happens, saprophyitic generally is referring to plants, a different set of roots are generally used for animals: detritivore
detri- decayed
-vore eating/nutrition