This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Mitochondria havea) Plasmid DNAb) Circular DNAc) Single stranded DNAd) Double stranded DNA 
Select and explain. 
A. bd, B. d, C. ab, D. ac
A: bd
Answer: A: bd 
Explanation: Mitochondrial DNA is small circular double stranded DNA molecule.