Difficult things to classify are what?
frontal zones Pollution not cells Allergies bacteria Leptospirosis rays or beams Pesticides
A B C D E F G H
Viruses Viruses are difficult to classify.
Difficult things to classify are not cells
Difficult things to classify are what? (A) frontal zones (B) Pollution (C) not cells (D) Allergies (E) bacteria (F) Leptospirosis (G) rays or beams (H) Pesticides