What is the usual type of DNA found in bacteria?

Bacteria have a simple cell structure with a single circular chromosome that contains their genetic material. The DNA in bacteria is double-stranded and circular, unlike eukaryotic cells, where DNA is double-stranded and linear and is associated with histone proteins. The circular DNA in bacteria is not associated with histone proteins. However, in the case of Mycoplasma species, the DNA is double-stranded and linear, which is an exception to the usual type of DNA found in bacteria. Therefore, the correct answer is option A, double-stranded and circular.