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: Microbiology
Which of the following viruses possesses DNA, a capsid with icosahedral symmetry and no lipid envelope -a) Herpesvirusb) Adenovirusc) Poxvirusd) Papovavirus 
Select and explain. 
A. c, B. bd, C. ab, D. ac
B: bd
Answer: B: bd 
Explanation: All nonenveloped viruses (whether DNA or RNA) have icosahedral symmetry.
Nonenveloped DNA viruses → PAP - PApova, Adeno, PArvo
Nonenveloped RNA viruses —› PCR - Picorna, Calci, Reo.

Also know

All DNA viruses (whether enveloped or nonenveloped) have icosahedral symmetry except poxvirus which has complex symmetry.
No DNA virus has helical symmetry.
RNA viruses have either icosahedral or helical symmetry :
Icosahedral symmetry → Nonenveloped RAN viruses (PCR → Picorna, Calci, Reo) and Retro, Flavi, Toga, (Remember - RFT).
Helical symmetry → Rest of the RNA viruses.