1.identifying characteristics of bacteria include

the presence and/or number of flagella
gram staining
shape and arrangement of cells
all of the above

The best and most correct answer among the choices provided by the question is the fourth choice "all of the above."

Bacteria vary from species to species, thus assigning many common traits to bacteria is difficult. Bacterialspecies are typified by their diversity. There are three notable common traits of bacteria, 1) lack of membrane-bound organelles, 2) unicellular and 3) small (usually microscopic) size.
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Where’s the selection?