RRB Group D GK Questions 2026

These are the oldest Indian coins, mostly silver pieces cut into irregular shapes and impressed with symbols punched one at a time, such as the sun, a six-armed wheel, hills, trees and animals.

Physiological density divides the total population of a region by the area of its cultivable or arable land, so it measures the pressure of all the people on the land that can actually grow food, and it is far higher than ordinary density in countries such as Egypt, where most…

Push factors are the unfavourable conditions of the place a person leaves, such as unemployment, poverty, crop failure, drought, flood, epidemic and political unrest; they push people out.

Natural growth is the increase that comes from the balance of births over deaths alone, so it is births minus deaths in the period, and it is negative when deaths exceed births.

Asia holds roughly three-fifths of all the people in the world, mainly in the two great clusters of East Asia and South Asia, which include the two most populous countries on earth.

The width of each bar in a population pyramid shows the share of that age group, so a broad base means that children form a very large part of the population, which happens where the birth rate is high; the narrow top shows that few people survive to old age.

In the first stage of the demographic transition the society is rural and agrarian, life expectancy is low, medical facilities are poor and literacy is low, so both the birth rate and the death rate are high and they roughly cancel each other, leaving population almost stationary.

Replacement level fertility is the total fertility rate at which a generation of women exactly replaces itself in the next generation.

The United Nations marked 15 November 2022 as the Day of Eight Billion, the date on which the world population was estimated to have reached eight thousand million.

In this essay of 1798 Malthus argued that population tends to increase in a geometric progression while the means of subsistence can increase only in an arithmetic progression, so growth must be restrained either by positive checks such as famine, disease and war, or by preventive checks such as late…

Density of population is a ratio between the number of people and the area they occupy, and the standard unit is the number of persons living in one square kilometre; it is the simplest way of measuring the pressure of people on land.

The law of conservation of mass, stated by Antoine Lavoisier in 1789, says that in a chemical reaction mass is neither created nor destroyed.

When copper is left in moist air for a long time, it slowly reacts with oxygen, water vapour and carbon dioxide.

On a hot day the air just above a road or desert sand is much hotter, and so optically rarer, than the air higher up.

At room temperature and normal pressure only two elements are liquids: mercury, a metal, and bromine, a non-metal. Mercury melts at about −39 °C and is used in thermometers and barometers because it stays liquid over a wide range and does not wet glass.

Potassium permanganate, KMnO₄, forms dark purple crystals that contain no water of crystallization; its formula has no attached water molecules.

This statement is wrong because bryophytes, the mosses and liverworts, have no true vascular tissue: they lack xylem to carry water and phloem to carry food.

A reducing agent is the substance that is itself oxidised while it reduces something else. In hydrazine, N₂H₄, nitrogen has an oxidation number of −2; in nitrogen gas, N₂, it is 0.

A p-type semiconductor is made by adding a small amount of a trivalent impurity, such as boron, aluminium, gallium or indium, to pure silicon or germanium.

Friction acts along the surfaces in contact, opposite to the direction of motion, not along the line joining the centres of two bodies, so it is non-central.