Explanation
1. The question asks which type(s) of micro-organisms are most widely used in industries.
2. Bacteria are extensively used in various industries, including food production (yogurt, cheese, vinegar), pharmaceuticals (antibiotics, vaccines), chemical production (enzymes, amino acids), and waste treatment.
3. Fungi (including yeasts and molds) are also crucial in industries like baking, brewing (yeasts), antibiotic production (e.g., Penicillium mold), enzyme production, and organic acid fermentation.
4. Micro-algae have applications in biofuel production, food supplements, and wastewater treatment, but their industrial use might be considered less widespread compared to bacteria and fungi in traditional industries as of 1998.
5. Considering the broad and established industrial applications, Bacteria, micro-algae and fungi (D) encompass the major groups widely utilized across various sectors. While algae's role might have been smaller then, including them covers more bases than option B.