What is the woman studying A: Silicon is much more uncommon than carbon. B: Carbon is much more common than silicon. C: Silicon is much more common.

Carbon chains can rotate around a double bond (carbon=carbon or C=C).

What caused the deposits A: The hydrochloric acid broke the carbon bonds in tile carbon dioxide, B: The magnesium oxide broke the carbon oxygen bonds in the carbon dioxide. C: The burning magnesium broke the carbon oxygen bonds in the carbon dioxide. D: The gas collection method broke the carbon-oxygen bonds in the carbon dioxid

______ of agricultural practices is a recognized method of carbon sequestration as soil can act as an effective carbon sink offsetting as much as 20% of 2010 carbon dioxide emissions annually.

The synonym of CO2 is .（ ）。 A: hydrogen B: carbon monoxide C: carbon dioxide D: oxygen

Carbon dioxide consists of carbon and （ ） A: oxygen B: emergency C: upgrade D: religious

are very soft ,and can be used for bolts and for machine parts that do not need strength.: Alloy steels|High carbon steels|Low carbon steels|Medium carbon steels

carbon emission

carbon dioxide

Questions 22-25 are based on the following passage. What is the "lead" in a pencil made of.’ A: Diamond. B: Carbon. C: Lead. D: Graphite.