(a) Deficiency of vitamins causes different human diseases. Choose the correct type of vitamin (Vit. A, Vit. B1, Vit. C, Vit. D, Vit. E, Vit. K) for each disease: 1. Poor night vision 2. Bleeding gums 3. Rickets in children 4. Beri-Beri 5. Anaemia. (b) People suffering from cardiovascular disease having high level of cholesterol in their blood, this often leads to build of fats on its internal arterial walls, suggest how this might be harmful to the heart. (c) Why the excessive use of chemical fertilizers should be avoided? (d) Why are Scientists worried about the increase of CO2 in atmosphere?

(a) Vitamin deficiency diseases

1. Poor night vision: Vitamin A 2. Bleeding gums: Vitamin C (scurvy) 3. Rickets in children: Vitamin D 4. Beri-beri: Vitamin B1 (thiamine) 5. Anaemia: Vitamin E

Note on anaemia: this is the best choice from the box, since a lack of vitamin E can break down red blood cells (haemolytic anaemia), particularly in premature babies. In everyday medicine, anaemia is more commonly linked with a lack of iron, vitamin B12 or folate, none of which are listed. Vitamin K deficiency causes poor clotting, and bleeding as a result.

(b) How fat build-up harms the heart

When LDL cholesterol is high, fatty deposits called plaques form inside artery walls, a process known as atherosclerosis. This harms the heart in several ways.

Narrowed coronary arteries: less blood, oxygen and nutrients reach the heart muscle. Chest pain (angina): the muscle suffers oxygen shortage, especially during effort. Blood clots: a plaque may rupture and a clot may form on it, suddenly blocking an artery and causing a heart attack, in which the muscle begins to die. Extra workload: stiff arteries raise blood pressure, so the heart must pump harder and can eventually weaken, leading to heart failure. Irregular heartbeat: damaged muscle can disturb the heart's rhythm.

(c) Why excessive chemical fertilizers should be avoided

Water pollution: excess nitrogen and phosphorus wash into rivers and lakes, where they cause algal blooms and low oxygen (eutrophication), killing fish. Groundwater contamination: nitrates can enter drinking water, and they are a particular risk to infants. Soil damage: heavy use can acidify soil, disturb useful microbes, and upset nutrient balance. Greenhouse gases: nitrogen fertilisers release nitrous oxide, a powerful greenhouse gas. Economic waste: crops cannot absorb nutrients beyond a certain limit, so the farmer pays for what is lost. Crop problems: excess nitrogen can produce weak growth and greater pest attack.

Balanced use based on soil testing, along with organic matter and crop rotation, gives better long-term results.

(d) Why scientists are worried about rising CO₂

CO₂ is a greenhouse gas that traps outgoing heat. Its concentration has risen from about 280 parts per million before industrialisation to over 420 ppm, chiefly from burning fossil fuels and deforestation. Scientists are worried for these reasons:

Global warming: more trapped heat raises the average temperature of the planet. Extreme weather: heatwaves, droughts, intense rain and floods are becoming more severe. Melting ice: glaciers and ice sheets shrink, and sea levels rise. Ocean acidification: the oceans absorb CO₂, which forms carbonic acid and harms corals and shellfish. Food and water security: crops, water supplies and ecosystems are put under stress. Long lifetime: a large part of emitted CO₂ stays in the atmosphere for centuries, so the damage is difficult to reverse.