Prehistoric chimpanzee species used tools similar to those used by pre

Conclusion: The tools must have been used by humans rather than chimpanzees
Premise: The area where the tools were found, however, is a savanna, and whereas there were prehistoric humans who lived in savanna habitats, prehistoric chimpanzees lived only in forests.
Just think what can be the possible assumption
1) In the prehistoric times there was no forest in Savanna
2) Prehistoric Chimpanzees can never came to human habitat

Let's POE

(A) IncorrectPrehistoric humans did not carry their tools with them when they traveled from one place to another.
Evem if they carry tool from one place to another place. it will not help us in any way to link the premis to the conclusion

(B) IncorrectSince the evolution of the first primates, East Africa has been predominantly savanna.

No way this this statement is helping us

(C) IncorrectPrehistoric humans never ventured into areas of the forest that were inhabited by prehistoric chimpanzees.
Let's negate this answer option "Prehistoric humans sometimes ventured into areas of the forest that were inhabited by prehistoric chimpanzees.Here one can see negated option is not shattering the conclusion in any way.
(D)Correct The area where the tools were found was not a forest at the time the tools were in use.
Just negate this option "The area where the tools were found was a forest at the time the tools were in use."
On negation negated option tells us that yes tool could be used by Chimpanzee and this negated version shatters our conclusion.
(E) IncorrectThe prehistoric ancestors of modern chimpanzees were not capable of using tools more sophisticated than those found recently in East Africa.
Irreverent to the context given
Hence D is correct

This might be true if they had carried their tools with them when trey travelled from their places to Prehisoric chimpanzee's places and left the tools there. Maybe true is incorrect. (A) is out.

Irrelevant.

This might be true only if they ventured into those area and left the tools there. Similar to (A). (C) is out.

This proves that Chimpanzees were not there when the tools were in use. Hang on to (D)

"more sophisticated": this leaves the possibilities that prehistoric chimpanzees were able to use less sophisticated tools. (E) is out.

Only D is left. D is the correct answer.