Which obligate, spore-forming anaerobe causes food poisoning in improperly canned foods?

The question asks to identify an obligate, spore-forming anaerobe that causes food poisoning in improperly canned foods.

• A) Campylobacter jejuni is a microaerophilic bacterium and does not form spores.
• B) Clostridium botulinum is an obligate anaerobe, meaning it grows in the absence of oxygen, and it forms spores. These spores can survive in improperly canned foods and produce a neurotoxin that causes botulism.
• C) Salmonella typhimurium is a facultative anaerobe and does not form spores.
• D) Staphylococcus aureus is a facultative anaerobe and does not form spores.

Therefore, Clostridium botulinum fits all the criteria described in the question.

The final answer is $\boxed{\text{B}}$.