Which of the following is not a common type of bacteria?

The correct response identifies "Hexacocci" as not being a commonly recognized type of bacteria. In the realm of microbiology, the types of bacteria are categorized based on their shapes and arrangements.

Streptococci, Bacilli, and Diplococci are all well-established terms used to describe specific bacterial shapes.

• Streptococci refers to spherical bacteria that form chains.
• Bacilli are rod-shaped bacteria, which can appear singularly or in chains.
• Diplococci are pairs of spherical bacteria.

In contrast, "Hexacocci" does not represent a recognized or categorized type of bacteria in scientific literature; the term is not commonly used to describe any bacterial configuration, as bacterial arrangements typically include singular, pairs, chains, or clusters but do not usually extend to hexagonal arrangements. Therefore, the identification of Hexacocci as not being a common type of bacteria is well-supported by the definitions and classifications found in microbiological studies.