T.O. Diener discovered a:

Options

(a) free infectious DNA
(b) infectious protein
(c) bacteriophage
(d) free infectious RNA

Correct Answer:

free infectious RNA

Explanation:

Theodor O. Diener discovered the Potato Spindle Tuber Viroid (“PSTVd”), the first viroid ever identified, in 1971. PSTVd is a small, circular RNA molecule. Dr. Diener discovered that the pathogen causing potato spindle tuber disease is not a virus, as previously believed, but a much smaller, free RNA molecule.