Mandarin Chinese is the most spoken language in the world with an estimated 845 million native speakers.
Yes it is possible to teach 'C', you can also learn it from a book but while learning you will need access to a computer with a 'C' compiler installed so that you can practice programming.
I'm not sure that "most used element" is a thing. Most used in what?Hydrogen is the most common element in the universe, but I have no idea what you mean by "most used."
the latest it was most used was the Superbowl!
The Penny is used the most in the US.
E is used the most.
French is used most in Quebec.
Youtube is the most used website in the world
Jesus is the most used word
Alcohol is the most used legal drug. Of Illicit drugs the most widely used drug is cannabis.
the Apollo 18 was the most used weapon by the Koreans.
Most routers can be used. The most popular used will probbaly be NetGear
The most used input device on a computer is the keyboard.