The Basel Convention, adopted in 1989, deals with which of the following?

The correct answer is C, vegetable peel. Biodegradable waste is waste that bacteria and fungi can break down into simpler substances within a short time, and kitchen waste such as vegetable peel is the classic example; it is exactly the wet fraction that Indian cities compost or send to a biogas digester. Option A is wrong because thermocol is expanded polystyrene, a plastic that microbes cannot digest, which is why it was included among the banned single-use items. Option B is wrong because aluminium foil is a metal; it does not rot, though it can be melted and recycled again and again. Option D is wrong because a polythene bag is a plastic that only fragments into smaller pieces and finally into microplastics, and may survive in soil and water for generations. The rule to carry into the exam hall is simple: anything that once lived, such as food, paper, cotton, leaves or dung, is biodegradable, while plastic, glass, metal and thermocol are not.

The correct answer is A, yellow. The yellow category covers human and animal anatomical waste, soiled waste such as dressings and cotton contaminated with blood, expired medicines and chemical waste, and this material is destroyed by incineration, plasma pyrolysis or deep burial; nothing from the yellow bin is recycled. Option B is wrong because the red bin takes contaminated recyclable plastic, such as tubing, catheters, urine bags, intravenous sets and syringes without needles, which is autoclaved or microwaved and then shredded for recycling. Option C is wrong because the blue category is meant for broken glassware, glass vials and metallic body implants, which are disinfected, washed and recycled. Option D is wrong because white, translucent, puncture-proof containers are reserved for sharps, that is, needles, scalpels and blades. Examiners usually set this as a match-the-pair question, so remember the four colours as one set.

The correct answer is A, smaller than 5 millimetres. Microplastics are plastic particles under five millimetres across, whether they were manufactured that small, as in cosmetic microbeads and synthetic textile fibres, or were formed when larger plastic articles weathered and broke up in sunlight and waves. Option B is wrong because five centimetres describes ordinary plastic litter, not microplastic; such pieces are visible and can still be picked up by hand. Option C is wrong because fifty microns is the scale of nanoplastics and fine fibres, far below the accepted cut-off, and no convention defines microplastics that way. Option D is wrong because a five-metre piece of plastic is macro litter such as a fishing net or a sheet. The importance of the five millimetre figure is biological: below that size plankton, fish and shellfish swallow the particles, so the plastic enters the marine food chain and comes back to human beings on the plate.

The correct answer is B, methane. In biomethanation, anaerobic bacteria break down organic matter inside a closed digester where no oxygen is present, and the gas they release is mainly methane, which is what makes biogas burn with a clean blue flame and gives it its fuel value. Option A is wrong because carbon dioxide is certainly present in biogas, but as the second component by volume, not the main one; it burns no further and only lowers the calorific value. Option C is wrong because nitrogen is at best a trace in biogas, coming from air leakage rather than from decomposition. Option D is wrong because sulphur dioxide is not produced in the digester; the sulphur impurity in biogas appears as hydrogen sulphide, which must be scrubbed out because it corrodes engines and pipes. The same methane forms slowly in a covered landfill, where it is called landfill gas and is either flared or tapped for power.

The correct answer is B, Extended Producer Responsibility. Under this idea a producer, importer or brand owner stays answerable for its product after the consumer has finished with it, and must arrange to collect back and recycle an agreed quantity of packaging or equipment; the plastic waste, e-waste and battery waste rules all run on it. Option A is wrong because the Environment (Protection) Act of 1986 and the rules made under it already carry their own names, and no waste rule uses the abbreviation for them. Option C is wrong because there is no statutory register by that name; effluents are regulated by consent conditions issued by the State Pollution Control Boards under the water law. Option D is wrong because energy recovery from refuse is called waste to energy or refuse-derived fuel, not EPR. Extended Producer Responsibility is best remembered as the working form of the polluter pays principle, applied to the maker rather than to the user.