Questions

This region is thus called because of its rich coal field and the iron and steel plants that have come up around them. Rhur valley is a major Industrial hub of West Germany. 

One grandfather, One father and One son makes two fathers and two sons.

Blotting paper absorbs ink by the process of capillary action. The capillary action is based on the property of surface tension of liquid.

All unsized paper will absorb water. Blotting paper is not sized and made bulkier to provide capillary action for faster absorption of liquid.

Blotting paper has also been sold as a cosmetic to aid in the removal of skin oils and makeup.

Pen names have had a certain place of their own in the world of writing. Pen names are something which every writer comes across at some time in their careers.

Indian author to use a pen name Bhanu Simha is Rabindranath Tagore. He also has Gurudev, Kabiguru as his pen names.

The common greenhouse gas containing only hydrogen and oxygen is H2O, this is water vapor.

The common greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

The composition (chemical formula) of those gases are:

Water vapor: H2O
Carbon dioxide: CO2
Methane: CH4
Nitrous oxide: NO
Ozone: O3.

As you see the only one of those that contains only hydrogen and oxygen is H2O, water vapor.