Explanation

Astronomers estimate a star’s age primarily by analyzing its chemical composition—especially the presence of hydrogen and helium.

Older stars generally have fewer heavy elements.  

Explanation

The form control used to select or deselect multiple options is a checkbox.

Each checkbox operates independently, allowing users to select as many options as needed from a list of choices. 

Explanation

 Prophet Muhammad (PBUH) abolished all pre-Islamic practices of usury (interest) and blood feuds/revenge killings

• The Prophet (PBUH) delivered his final sermon during the Hajj on Mount Arafat.
• It is also known as Farewell Sermon.
• The Holy Prophet (SAW) performed Hajjat-ul-Wida in the 10th Hijri.
  
• It was performed on Friday, the 9th of Dhu al-Hijjah (March 6, 632 A.D).
• This final pilgrimage included his renowned Farewell Sermon.

Explanation

Magnetic Bubble Memory was an early non-volatile memory technology from the 1970s

That stored data as magnetic domains ("bubbles") in a thin film of magnetic material.

It was a mechanically addressed system, and data access involved physically moving the bubbles past a read/write head

Explanation

A Mutawatir Hadith is narrated by so many people at each stage that it is inconceivable they all agreed to lie.

This ensures its authenticity.

Explanation

The correct preposition is "to" — we say "a preface to a book." 

He has written a preface to this book.

Explanation

Lake Malawi is primarily located in the country of Malawi,

But it is also bordered by Mozambique and Tanzania.

Malawi contains the largest portion of the lake, which covers about one-fifth of the country's total land area. 

It is the fourth-largest freshwater lake in the world by volume,

The ninth-largest lake in the world by area

The third largest and second deepest lake in Africa.

Explanation

A monitor is used as a VDU (Visual Display Unit). 

 A VDU refers to the device that displays visual output from a computer, and a monitor is the primary device used for this purpose. 

Explanation

Hard disks are considered long-term memory in a computer because they retain data even when the computer is powered off,

Unlike RAM (Random Access Memory) which is volatile and loses data when the power is off. 

Explanation

The Pakistan Environment and Protection Agency is now called the Pakistan Environmental Protection Agency, often abbreviated as Pak-EPA.

The agency operates under the Pakistan Environmental Protection Act (PEPA) 1997. 

Formed November 9, 1997