Tag: science & technology

Marble is a metamorphic rock formed from limestone undergoing intense heat and pressure. Metamorphic rocks are transformed from existing rock types. Igneous rocks form from cooling magma, sedimentary rocks from accumulated deposits, and conglomerate is a specific type of sedimentary rock.

Bauxite is the principal ore of aluminium, containing aluminium hydroxide minerals like gibbsite, boehmite, and diaspore. It is the primary source of aluminium metal production worldwide. Haematite is an iron ore, while aluminite and alumina are not standard ore names (alumina is aluminium oxide produced from bauxite).

Red blood cells (erythrocytes) are produced in the bone marrow through a process called erythropoiesis. In adults, this primarily occurs in the flat bones like the sternum, ribs, and pelvis. The liver produces red blood cells only during fetal development, while the spleen filters and stores old red blood cells rather than producing them.

Nephritis is the medical term for inflammation of the kidneys, from the Greek word 'nephros' meaning kidney. It can be caused by infections, autoimmune conditions, or toxins. The other options are made-up terms - 'Kidneyitis' uses English words, 'tubulitis' would refer to tubules not kidneys, and 'renalitis' mixes Latin and Greek roots incorrectly.

The diameter of a circle or sphere is exactly twice its radius. If Earth's radius is 6370 km, then diameter = 2 × 6370 = 12740 km. Option A (12720) is very close to this calculation. The small difference might be due to rounding or using slightly different values for Earth's average radius.

The thermosphere is the warmest layer of Earth's atmosphere, with temperatures reaching up to 2,500°C due to absorption of intense solar radiation. Despite these high temperatures, the air is so thin that it would feel cold to human skin. The troposphere is where we live and where weather occurs, while the stratosphere contains the ozone layer.

The Sun is primarily composed of hydrogen (about 73% by mass) and helium (about 25% by mass), with trace amounts of heavier elements. These two elements fuel the nuclear fusion reactions in the Sun's core that produce its energy. The notation 'H and He' correctly identifies these two dominant elements.

While the Milky Way's galactic center (which likely hosts a supermassive black hole) has extremely strong gravity, the question's phrasing is problematic. Gravity at the center of a black hole is infinite according to general relativity (singularity), making this a theoretical rather than measurable comparison. Jupiter has the strongest surface gravity of planets in our solar system, but black hole gravity far exceeds anything else.

Mass is an intrinsic property of matter and does not change with location. A 42 kg mass on Earth remains 42 kg on the Moon - only the weight (force of gravity acting on that mass) changes. Weight would be about 1/6th on the Moon (approximately 7 kg force), but mass stays constant at 42 kg.