Answer :
A probiotic supplement should contain a variety of bacterial strains. Hence, the correct option is D.
To understand which statement is true about probiotic supplements, let's inspect each option:
1. "They are all the same." This statement isn't accurate. The composition of probiotic supplements can vary significantly based on the strains of bacteria they contain, their strength (CFU count), and the additional ingredients included.
2. "They are measured in mg or micrograms." This is also not correct. Probiotics are typically measured in Colony Forming Units (CFU), which represents the number of viable bacteria.
3. "They should contain a variety of bacterial strains." This statement is indeed true. Most effective probiotic supplements often contain multiple strains of bacteria, as different strains can offer different health benefits. A probiotic with a diverse selection of strains can provide more comprehensive gut health support.
Hence, the correct option is: "They should contain a variety of bacterial strains."
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