Which of the following statement is true how fossil records can produce incomplete evidence of organisms that lived on Earth? Small plants and animals found on Earth were not fossilized.
Not all organisms that lived on Earth have been fossilized.
Large plants and animals found on Earth were not fossilized.
There are fossils that we cannot identify.

Answer

i think b                          

they making me put 20 characters  so dont mind what you reading lol                    

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol