Questions

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.

Ayurveda Owes its Origin to Atharvaveda.

The early history of ayurveda asserts that around 1500 BC, ayurveda's fundamental and applied principles got organised and enunciated. In this historical construction, Ayurveda traces its origins to the Vedas, Atharvaveda in particular, and is connected to Hindu religion. Atharvaveda (one of the four most ancient books of Indian knowledge, wisdom and culture) contains 114 hymns or formulations for the treatment of diseases. Ayurveda originated in and developed from these hymns. In this sense, ayurveda is considered by some to have divine origin. Indian medicine has a long history, and is one of the oldest organised systems of medicine. Its earliest concepts are set out in the sacred writings called the Vedas, especially in the metrical passages of the Atharvaveda.

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

Functional testing is a type of testing that is done against the requirements of the business application. 

Examples of functional testing are Smoke testing, Sanity testing, Regression testing, Usability testing.