Best answer gets
which of the following is a distraction that you find when photographing animals at the zoo?

fences
enclosure glass
other people
all of the above

All of the above are distractions that you find when photographing animals at the zoo. 

Fences clearly will immediately block your field of view and it can be challenging to photograph the animals when it is a stationary object that can not be avoided in any scenario. 

While enclosure glass may be transparent, there is a certain amount of glare and scratches that can be visible and make it harder to photograph the animals or even tarnish the end result. 

Other people passing by can make it difficult to photograph things at the exact right time as they get in the way of your photograph and this can not always be avoided. 

Riffin tells a story about photographing elephants in a wildlife sanctuary in africa. he says that the photographer brought back more than just an amazing story.