Explanation

The homogeneous equation ax² + 2hxy + by² = 0 represents:

• A pair of real and distinct straight lines through the origin if h² − ab > 0
• A pair of coincident lines if h² − ab = 0
• A pair of imaginary lines if h² − ab < 0

So, the correct answer is: h² − ab > 0

Explanation

Relevant means قریب سے منسلک یا ہاتھ میں معاملے سے مناسب

Concerned means کسی چیز سے رشتہ یا تعلق

Explanation

 As a reaction proceeds, the rate of reaction decreases because the concentration of reactants decreases, leading to fewer collisions and slower reaction. 

Explanation

 Coralline red algae are the type of algae that play a role in building coral reefs, along with coral animals.

These algae secrete and deposit calcium carbonate,

Which helps to cement the reef structure together

Explanation

Parvoviruses are among the smallest DNA viruses, with a typical diameter of around 18–26 nanometers (nm).

So, 20 nm is the most accurate option from your list.

Explanation

The hypothalamus is a part of the brain that acts as the body's thermostat, regulating body temperature by adjusting heat production and heat loss to maintain a stable core temperature. 

Explanation

Explanation

In Bohr's model, electrons occupy specific energy levels around the nucleus.

When an electron moves from a lower energy level to a higher energy level, it absorbs energy

Conversely, when an electron moves from a higher energy level to a lower energy level, it emits energy.

This energy is emitted as a photon of light with a specific wavelength, corresponding to a specific frequency. 

Explanation

The dead time of a GM counter is the brief period (about 10⁻⁴ seconds) after detecting a particle during which it can't detect another.

This happens because the detector needs time to reset.

It limits how fast the counter can measure radiation.

Explanation

Original statement: p → q

Contrapositive:  ¬q → ¬p

Converse of contrapositive: Swap it → ¬p → ¬q