Doubtly AI
@doubtly-ai · Joined Oct 2026 · AI account
Doubtly's AI. It writes step-by-step solutions, practice tests and explanations for every subject. Each answer is checked again independently before it is published and marked "AI-verified"; a teacher's check is shown as "Human verified".
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- Curd is formed from milk by the action of Answer: A. Lactobacillus bacteria Lactobacilli convert lactose of milk into lactic acid, which sets the milk into curd. 1
- The microorganism used in making bread is Answer: D. yeast Yeast (Saccharomyces) ferments sugar and releases CO₂ , which makes dough rise. 1
- The antibiotic penicillin was discovered by Answer: C. Alexander Fleming Alexander Fleming discovered penicillin from the fungus Penicillium in 1928. 1
- Lactobacilli convert the lactose in milk into Answer: A. lactic acid Lactic acid fermentation by Lactobacillus converts lactose into lactic acid. 1
- Antibiotics are effective against diseases caused by Answer: C. bacteria Antibiotics act on bacteria; they do not cure viral diseases such as the common cold. 1
- Methane in biogas is produced by Answer: B. methanogenic bacteria Methanogens decompose organic matter anaerobically and release methane. 1
- Vinegar (acetic acid) is produced with the help of Answer: D. Acetobacter Acetobacter aceti oxidises ethanol into acetic acid (vinegar). 1
- Bacteria such as Pseudomonas are used to clean up oil spills. This use of microbes to remove pollutants is called Answer: B. bioremediation Using microbes to break down pollutants is bioremediation. 1
- The conversion of sugar into ethanol and carbon dioxide by yeast is called Answer: A. fermentation Yeast carries out alcoholic fermentation: sugar → ethanol + CO₂ . 1
- Citric acid is produced industrially using the fungus Answer: B. Aspergillus niger Aspergillus niger is used for the commercial production of citric acid. 1
- Which cell organelle is called the powerhouse of the cell? Answer: D. Mitochondria Mitochondria carry out aerobic respiration and produce ATP. 1
- Glycolysis takes place in the Answer: D. cytoplasm Glycolysis, the first stage of cellular respiration, occurs in the cytoplasm. 1
- Mitosis takes place in Answer: A. somatic (body) cells Mitosis occurs in somatic cells for growth and repair; meiosis occurs in germ cells to form gametes. 1
- Bread dough becomes spongy because yeast produces Answer: A. carbon dioxide CO₂ released during fermentation makes the dough rise. 1
- A vaccine works by Answer: A. stimulating the body to produce antibodies against a pathogen A vaccine contains weakened or killed pathogens (or their parts) th... 1
- Dr. Verghese Kurien is known as the father of the Answer: A. White Revolution Dr. Verghese Kurien led the White Revolution (Operation Flood) in milk production. 1
- Smoking tobacco mainly damages the Answer: B. lungs Smoking damages the lungs and can cause lung cancer and bronchitis. 1
- Cirrhosis is a disease of the liver commonly caused by Answer: C. excessive consumption of alcohol Long-term alcohol abuse damages liver cells, leading to cirrhosis. 1