Which one of the following food contaminations would be suspected if the end of a can of tomatoes had begun to swell?
a. botulism
b. e. coli
c. salmonella
d. acidophilus

The answer is A. Botulism. 

Normally, botulism would occur in less acidic canned foods but it's possible with tomatoes. 

Another cause of can swelling is when high acidic food starts to attack the can and hydrogen gas is released causing the can to swell. 

“d” is the answer to the question