1. carbon cycle
all of the physical processes and chemical reactions that result in the movement of carbon between the biosphere (living forms) and the geosphere (water, earth, and atmosphere)
2. carbon footprint
an overall increase in world temperatures that may be caused by additional heat being trapped by greenhouse gases
3. global warming
components of the air mixture that trap infrared (heat) energy
4. greenhouse gas
a calculation that considers an individual's contribution to the process of global warming based on activities leading to greenhouse gas production

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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