Answer: The correct answer is -
D) Some bacteria are beneficial to humans and some bacteria are harmful.
Bacteria are prokaryotic organisms that do not contain a defined nucleus and membrane bound subcellular compartments (called cell organelles).
Certain bacteria are beneficial to human lives whereas other bacteria are harmful.
For example - Lactobacillus bacteria that is present in the dairy product is useful for the human health as it maintains the gut microbiota, providing good health.