Which statement is correct?
A) All bacteria are autotrophic
B) All bacteria are heterotrophic
C)All bacteria are photosynthetic
D) Mostly bacteria are heterotrophic but some autotrophic.

Hint: Bacteria can be photosynthetic or chemosynthetic autotrophs or saprophytes or parasitic.Though, they cannot obtain energy directly from their food because they do not have a mitochondrion.

Complete Answer:
1) Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists, and many parasitic plants. Other organisms, called heterotrophs, take in autotrophs as food to carry out functions necessary for their life.
2) Autotrophs are known as producers because they are able to make their own food from raw materials and energy. Examples include plants, algae, and some types of bacteria. In other words, autotrophs get their carbon directly from carbon dioxide, which they use to create organic carbon compounds for use in their own cells.
3) Heterotrophs All animals, almost all fungi, as well as most bacteria and protozoa depend on autotrophs, or primary producers, for the raw materials and fuel they need.Heterotrophs are known as consumers because they consume producers or other consumers. Dogs, birds, fish, and humans are all examples of heterotrophs.
4)Heterotrophic bacteria include all bacteria that use organic nutrients for growth. These bacteria are universally present in all types of water, food, soil, vegetation, and air. However, Bacteria can be photosynthetic or chemosynthetic autotrophs or saprophytes or parasitic.
As we can see from the discussion, most bacteria are heterotrophs while some are photo or chemosynthetic autotrophs.

Therefore, the correct answer is option D (Mostly bacteria are heterotrophic but some autotrophic).

Note: We can get an infection when bacteria enter into our body. So, you can get a bacterial infection when bacteria enters into your body through an opening in your skin, such as a cut, a bug bite, or a surgical wound. Bacteria may also enter your body through your airway and cause infections like bacterial pneumonia.