The plants that never produce flowers are called "cryptogams." Cryptogams include plants such as ferns, mosses, liverworts, and algae. Unlike flowering plants (angiosperms), which reproduce through seeds enclosed within flowers, cryptogams reproduce through spores and do not produce true flowers. Cryptogams are considered more primitive in evolutionary terms compared to angiosperms, which are the most dominant group of plants on Earth today.

The North rop Grumman B-2 Spirit also known as the stealth technology designed for penetrating dense antiaircraft defenses. It is able to deploy both conventional and nuclear weapons.

This is a fundamental constant in chemistry that represents the number of atoms or molecules in one mole of a substance. (Option 4 is correct) Its value is approximately 6.022 x 10²³, and it is denoted by the symbol "N_A". Avogadro's number is a key concept in stoichiometry. The branch of chemistry deals with the quantitative relationships between reactants and products in chemical reactions.

A falling barometric pressure, detected by a barometer, signals an approaching thunderstorm. This drop indicates unstable atmospheric conditions, often preceding stormy weather. Meteorologists use barometric readings to predict thunderstorms, as the decrease in pressure signifies the likelihood of imminent weather disturbances and allows for timely weather warnings.