What happened when griffith injected mice with the harmless, r-strain bacteria alone?
a. the bacteria transformed.
b. the mouse lived.
c. the mouse died.
d. the bacteria died.

Option B, The mouse lived.

Explanation:

In Griffith's experiments three major observations were made -

a) Injecting the mice with S - strain bacteria - The S - strain bacteria's were infected bacteria's and hence when these S -bacteria's  were injected into the mice ,they were killed due to infection.

b) Injecting with R -strain harmless bacteria - These being harmless did not affected the mice and hence they remained healthy and alive

c) Injecting heated S -strain into R -strain infected mice - These mice also developed the disease due to virulent remains of heated S -strain affecting the R -strain.

Hence, option B is correct

the answer to your question is tooth decay.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.