Dr. garvey measured the ph inside a bacteria cell and found the ph was a level 4. she then injected enough acid into the cell to change the ph to a level 2. she re-measured the ph after several moments and found the bacteria cell remained at ph of 4. what is the most likely explanation?

a. the bacteria cell contained enzymes which changed the ph
b. she made a mistake and injected the wrong acid
c. the bacteria cell contained sugars which increased the ph
d. the bacteria cell contained buffers which regulated the ph