________ may become louse-infested under suitable conditions.

Mycobacterium tuberculosis is classified as a

A) nonphotochromogen. B) scotochromogen. C) photochromogen. D) none of the above

There is ____ in the overall crude death rate in the United States from the year 1900 until 1996.

A. a definite increase B. a slight decrease C. hardly any change D. a clear decline