metals are the elements that easily make electrons by giving up electrons. And form metallic bonds with atoms of metals.
The Indus Valley Civilization is also called Harappan civilization and Indus-Saraswati civilization. It developed along the banks of the Indus and Ghaghghar.
Greenhouse gases are naturally present in the atmosphere and are also essential for life on earth. But, unfortunately due to industrial revolution there has been a huge increase in the emission of greenhouse gases in the atmosphere.