Which statement best captures a limitation of many commercial probiotic supplements highlighted in the lesson?

They always permanently colonize the gut and therefore require only a single dose to replace dietary measures such as fiber intake for life.

They are identical to fermented foods in composition and effect, so there is never any reason to consume whole fermented foods when supplements are available.

They often deliver large quantities of one or a few strains, which may offer specific benefits but do not substitute for maintaining a naturally diverse microbiome supported by varied dietary fibers.

They are universally harmful because any introduced microbe immediately causes inflammation and should never be used under any circumstances.