A Colony of Mice Is Treated with a Nonvirulent Strain

A colony of mice is treated with a nonvirulent strain of the bacterium Streptococcus pneumoniae . Before treatment, a researcher exposed this nonvirulent strain to heat-killed cells of a virulent strain. What will be the effect on the mouse population?

A) The mice will all remain healthy.
B) Some mice will develop a paralytic condition, but most will remain healthy.
C) Most or all of the mice will develop pneumonia.
D) Some mice will develop pneumonia, but most will remain healthy.
E) The mice will become immune to the bacteria.