An idea most likely to represent “common knowledge” if

An idea can be considered as common knowledge

When all involved in the research or study are aware of the fact and on the same front also know that fact is common and is known to everyone. Also a common knowledge is not cited anywhere and is believed to be easily acceptable. Some  examples of “common knowledge are –  

a)There are 12 months in a year

b)Obama was the president of America

Common knowledge is to know about the general information about anything which is widely known or easily verified. It is nothing unusual, instead, it is the most general knowledge or awareness about a certain statement or evidence which would reliably be accepted by the average educated reader without having to look up. General knowledge can be said as Pyramids are one of the seven wonders of the world and English is the most common language used worldwide.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

i don't know. if i were you, i would search it up online : d