Which type of bacteria is arranged in pairs and commonly associated with pneumonia?

The type of bacteria that is arranged in pairs and is commonly associated with pneumonia is diplococci. These bacteria are characterized by their spherical shape and tendency to link together in pairs. Specifically, the genus Streptococcus, which includes pathogens such as Streptococcus pneumoniae, is a prime example of diplococci. This particular bacterium is a major causative agent of pneumonia, making this answer correct.

Understanding the arrangement and classification of bacteria is essential in microbiology, as it assists in identifying the type of infection and the appropriate treatment. Other bacteria listed, such as streptococci and staphylococci, do not specifically refer to the paired arrangement associated with diplococci. Bacilli refers to a rod-shaped bacteria, which is distinct from the spherical shape of diplococci. Thus, the characteristics of diplococci align accurately with the context of the question regarding pneumonia.