The results of carbohydrate fermentation testing using maltose with phenol red as an indicator are shown below.

The results of carbohydrate fermentation testing using maltose with phenol red as an indicator are shown below. Which of the tubes shows the result from a bacterial species that does not produce hydrogen as a by-product of its ability to ferment maltose?

a.      A

b.     B

c.      C or E

d.     D

e.     None of the above