Final answer:
Bromothymol blue with a pH range of 6.0-7.6 is the correct pH indicator used for Glucose, Lactose, Raffinose Test as it changes color to indicate a drop in pH due to acid production from fermentation.
Step-by-step explanation:
To determine which pH indicator is used for Glucose, Lactose, Raffinose Test and its pH range, we need to consider the pH at which these sugars are generally fermented by microbes. Once the sugars are fermented, they produce acid that lowers the pH of the medium. The chosen pH indicator should change color within this acidic range to indicate whether fermentation has occurred.
The correct answer is A) Bromothymol blue, with a pH range of 6.0-7.6. It is a suitable indicator for observing fermentation in media containing the sugars glucose, lactose, or raffinose, as it will change color to indicate a drop in the pH due to acid production from fermentation.
Other indicators, such as phenol red and methyl red, have different pH ranges and color changes; thus, they may not be as suitable depending on the expected pH range after fermentation of the sugars in the specific test.