Final answer:
Statement B, which states the normal intestinal microbiota can help aid digestion and absorption of nutrients, is true. The intestinal microbiota also assists in protecting against pathogens and contributes to nutrient production but is potentially harmful if microbes colonize different tissues.
Step-by-step explanation:
The normal intestinal microbiota plays a crucial role in overall health and digestion. B. It can help aid digestion and absorption of nutrients is the correct statement.
These microbes, which include various species of bacteria, archaea, and fungi, assist in nutrient production, such as vitamin B12, folate, riboflavin, and vitamin K, and in breaking down food.
They also act as a primary line of defense against pathogenic organisms through competitive exclusion and other mechanisms, such as the production of bacteriocins.
It's important to note that while these microorganisms are typically harmless when confined to the gastrointestinal tract, they indeed can cause harm if they colonize different tissues.
Additionally, the microbial diversity within the intestines is much larger than a couple of dozen species; it's a vast and complex community. Furthermore, the intestinal microbiota comprises not just bacteria, but also archaea, fungi, protists, and viruses. Hence, statement D is incorrect.