Right choice is (a) Fungi
For explanation I would say: Probiotics are live bacteria and yeasts that are good for your health, especially your digestive system. Example – Lactobacillus species (L. acidophilus, L. casei, L. reuteri, L. bulgaricus, L. plantarum, L. johnsonii, and L. lactis), Bifidobacterium species (B. bifidum, B. longum, B. breve, B. infantis, B. lactis, and B. adolescentis), and others microbes like Bacillus cereus, Non pathogenic Escherichia coli, Saccharomyces cerevisiae, Enterococcus faecalis, and Streptococcus thermophilus.