The passage uses the term "vegetative forms" to refer to （）

A. Plants that infest human habitations
B. the fact that bacteria are really vegetables
C. the growing stage of the bacteria as opposed to the dormant stage
D. the difficulty in classifying the types of bacteria

The vegetative forms of most bacteria axe killed by drying in air, although the different species exhibit pronounced differences in their resistance. The tubercle bacillus is one of the more resistant, and vibrio cholcra is one of the more sensitive to drying In general, the encapsulated organisms are more resistant than the non-encapsulated forms. Spores are quite resistant to drying; the spores of the anthrax bacillus, for example, will germinate alter remaining in a dry condition for years or more. The resistance of the pathogenic forms causing disease of the upper respiratory tract is of particular interest in connection with airborne infection, for the length of time that a droplet remains infective is a result, primarily, of the resistance of the particular microorganism to drying.