Final answer:
The true statement about bacterial plasmids is that A) they are small circular DNA molecules that can replicate autonomously. They often carry genes that confer advantageous traits, such as antibiotic resistance, and are used in genetic engineering.
Step-by-step explanation:
The correct statement regarding bacterial plasmids is A) They are small circular DNA molecules that can replicate autonomously. Plasmids are extrachromosomal DNA found in prokaryotic cells such as bacteria and are distinct from the chromosomal DNA located in the nucleoid. These small, circular, double-stranded DNA molecules can carry genes that provide advantageous traits like antibiotic resistance. Unlike chromosomal DNA, plasmids can be transferred between bacteria, aiding in the spread of beneficial traits through horizontal gene transfer. Although plasmids can carry essential genes for survival under certain conditions, they typically do not carry genes for essential metabolic functions of the cell. However, they are a vital tool in genetic engineering and biotechnology due to their ability to replicate autonomously and carry foreign DNA fragments into bacterial hosts.