Microorganisms are our friends and foes. Some of them are useful for us while some of them are harmful. From the given list sort out useful and harmful actions of microorganisms.
Production of antibiotics, food spoiling, curd preparation, vaccine production, citrus canker.

The correct option is B Useful: Production of antibiotics, curd preparation, vaccine production

Harmful: Food spoiling, citrus canker

An antibiotic is a chemical substance that inhibits the growth of bacteria. They hinder the reproductive cycle of the bacteria inside the body of the host.
Lactobacillus is a genus of bacteria, which can convert sugars into lactic acid by means of fermentation.
A vaccine is a biological preparation that provides active acquired immunity to a particular disease. It has killed or weakened suspension of microorganism which generates the immune response.

Citrus canker is a disease affecting citrus species caused by the bacterium Xanthomonas axopods. The infection causes lesions on the leaves, stems, and fruit of citrus trees, including lime, oranges, and grapefruit.

Micorganism like fungus releases toxins which spoils the food.

So, the correct answer is option B.