Answer
The correct options are in the order : d,e,b,f,g,a,c
Work Step by Step
methanogen - d. releases methane gas
nucleoid - e. region with DNA
retrovirus - b. has RNA genome, protein coat
plasmid - f. circle of nonchromosomal DNA
extreme halophile - g. salt lover
viroid - a. infectious RNA
sex pilus - c. draws cells together