Most likely the first person
The answer should be A.
Why?
“Different type of atoms” which refers to different element present in the compound. Only Barium, Oxygen, and Hydrogen found in that compound, thus there are 3 types of atom founded it hydrated barium hydroxide.
I hope this enlighten. Apologize for any English or Chemistry concepts.
Answer:

Explanation:
Florine has the highest electronegativity and it thus pulls the element of
groups in the COOH group towards itself, making it relatively easy to loose the proton of the carboxyl group.
F O
↑ ||
F← C ← C ← O - H , Here three Florine withdraw
↓
F
F O
↑ ||
F← C ← C - O H , Here two Florine withdraw
↓
H
F O
| ||
H - C - C - OH , Here one Florine withdraw
↓
H
H O
| ||
H - C - C - OH , Here no Florine withdraw
|
H
Is found in both the living portion of our planet and the inorganic parts of the earths system