While theorists over the years have been unable to form a universal definition of intelligence, it has become clear that human intelligence is

"variable"

Explanation:

According to my research all theorists believe that it is a clear observation that human intelligence is "variable". This is because thousands of different situations and/or variables can affect a persons intelligence growing up. Also, genetics (DNA) can affect a child's intelligence as well. Therefore since there are too many things that can affect/determine a persons intelligence theorists consider it to be "variable"

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can you explain it better

not  

cuba  

russia  

iraq  

el salvador  

explanation:

known as the land of volcanoes, el salvador has visit seismic tremors and volcanic movement. it is the main nation in central america that does not have a coastline on the caribbean sea. about portion of all salvadorans live in the wide open. they are poor and don't have power or running water in their homes. in 1525, pedro de alvarado, a lieutenant of cortés's, vanquished el salvador. el salvador, with alternate nations of central america, pronounced its freedom from spain on sept. 15, 1821, and was a piece of a league of central american states until the point when that association broke up in 1838.