D. Most known bacteria have their genomes sequenced and the genes functions are known.
A. The statement "It has only adenine, uracil, cytosine, and guanine" is incorrect as it implies that bacterial DNA is different from other organisms' DNA. In reality, all DNA, including bacterial DNA, contains the four nitrogenous bases adenine, thymine, guanine, and cytosine.
B. The statement "Usually not sequenced because it requires copious resources and time" is also incorrect. In fact, bacterial DNA is often sequenced because it is relatively simple and straightforward compared to the DNA of more complex organisms like humans. With advances in technology, sequencing bacterial DNA has become faster and more affordable.
C. The statement "It has all the information for the structure and function of a cell" is partially true but not specific to bacterial DNA. The DNA genome in all organisms provides the genetic information necessary for the structure and function of a cell.
The best statement that describes bacterial DNA is actually the one provided in the question, which states that "Since the beginning of genome sequencing around two decades ago, most of bacterial genomes have been sequenced and their functions known." This is because, as noted by Donkor (2013), there has been a significant effort in recent years to sequence and study bacterial genomes, resulting in a wealth of knowledge about bacterial DNA and its functions.