The Grand Canyon is a spectacular sight. The Colorado River flows at the bottom of the deep, wide canyon. When we see the Grand Canyon today we see the result of А
deposition by wind that added material to the canyon walls over millions of years.
B
water erosion that wore away the canyon walls over millions of years.
C
deposition by water that added material to the canyon walls over millions of years

elements make up everything, and they combine to make compounds.

the answer is c

it’s previous models   because when i picked that son of a gun’s answer it was wrong look for previous models because they might make it a different letter  

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