Explanation

 That was the worst movie I have ever seen.

"Worst" is the superlative form of "bad" and is used to describe something that is the worst out of a group or over time.

The phrase "I have ever seen" indicates a comparison over all time, which requires a superlative form.

Explanation

The IUPAC name of iso-octane is 2,2,4-trimethylpentane. 

Explanation

Simple harmonic motion (SHM) is also known as oscillatory motion or periodic motion.

It can also be referred to as harmonic oscillation.

It is a system exhibiting SHM that is often called a simple harmonic oscillator. 

Explanation

In semiconductors, when an electron leaves its position in the valence band, it creates a "hole" which can act as a positive charge carrier.

This is why holes are primarily associated with semiconductors. 

Explanation

 The brave do not yield to the enemy.

بہادر دشمن کے سامنے نہیں جھکتے۔

"Yield to" is a common phrase meaning to surrender or give in to someone or something.

In this sentence, it means the brave do not surrender to the enemy.

Explanation

An insulator has a completely filled valence band. 

Explanation: In an insulator, all the valence electrons are tightly bound to their atoms and cannot move freely, resulting in a filled valence band.

Since there are no electrons available in the conduction band, they cannot move to it and conduct electricity. 

Explanation

The exchange of parts of non-sister chromatids of homologous chromosomes during meiosis is called Crossing over. 

During meiosis, homologous chromosomes pair up and "cross over," exchanging genetic material between their non-sister chromatids, resulting in new combinations of alleles. 

Explanation

The force of attraction between helium atoms is the London dispersion force. 

Helium is a non-polar noble gas, so the only force of attraction between its atoms is the weak London dispersion force, which arises from temporary fluctuations in electron distribution. 

Explanation

 The direction of a vector in space is typically specified by three angles.

These angles, often referred to as azimuth, elevation, and tilt (or polar/inclination), describe the vector's orientation in 3D space relative to a chosen reference frame.