The great Sahara Desert created an opportunity for wealth by trading to peoples who live in and around the region. The city of Timbuktu was built as a result of this trade.

Hundreds of years ago, salt was a very valuable commodity. It was valued for its taste as well as its ability to preserve food. One of the most productive areas for producing salt was the Sahara Desert, and the city of Timbuktu was built to capitalize upon this trade.

Pest infestation is nothing but the presence of large number of pests at a place, typically so as to cause damage or disease.

Climatic conditions affect a considerable number of pests. Some are more active during warmer periods than others. As these summer insects invade your home, they're likely in search of food, water, shelter, or have encountered an entrance. To pest-proof your home this summer, it's best to remove their 'WHY’ or reason for entering your home.

* Keep your place clean and dry. Make sure there is no food laying about.

* Removing food residue - food is a common attraction to a number of different pests.

* Regular disinfection of the surfaces.

Mercator projection type of maps are best suited for maritime navigations.

Silver is the best conductor of both heat and electricity among metals with a thermal conduction value of about 430 W/(mK).

Gold and copper both come respectably close to silver.

Copper being significantly less costly it is often chosen over silver in many applications.

The relative pronoun acts as the subject or object of the relative clause. It replaces words like she, he, him, her, they, them etc.

It is, therefore, wrong to repeat the pronoun in the relative clause.

Hence, the correct sentence is Shreya, who is my best friend, is a singer.

Gene is a segment of chromosomal DNA or a sequence of DNA or RNA that codes for a molecule that has a function. It is the basic physical and functional unit of heredity.

As genes are made up of DNA it impies that they are long, double chains of nucleic acids as DNA is made of nucleic acids.

All of us, believe that the Solar System evolved from a giant cloud of dust and gas. They believe that this dust and gas began to collapse under the weight of its own gravity. As it did so, the matter contained within this could begin moving in a giant circle, much like the water in a drain moves around the center of the drain in a circle.

At the center of this spinning cloud, a small star began to form. This star grew larger and larger as it collected more and more of the dust and gas that collapsed into it.

Further away from the center of this mass where the star was forming, there were smaller clumps of dust and gas that were also collapsing. The star in the center eventually ignited forming our Sun, while the smaller clumps became the planets, minor planets, moons, comets, and asteroids.

The best example for somatic mutation would be cancer, familial cancer (which transmits through gametes to the next generation) are not so common while sporadic cancer is seen the most where body cells of a particular area goes through mutations for a number of years and becomes cancerous, but it is not transmitted to next generation.