Step 1: Understanding the Concept:
Kefir is a fermented milk product.
It uses a specific combination of microorganisms.
Step 2: Key Formula or Approach:
No specific formula.
Need to know the microorganisms in Kefir.
Step 3: Detailed Explanation:
Lactobacillus reuteri and Lactobacillus caucasicus are used in Kefir.
These are part of the kefir grains.
L. gasseri and L. helveticus are used in other products.
Lactococcus lactis is used in cheese and buttermilk.
Thus, the correct species are L. reuteri and L. caucasicus.
Step 4: Final Answer:
Lactobacillus reuteri and Lactobacillus caucasicus are used in Kefir.
Hence, the correct option is (A).
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