which compound can be used to preserve biological specimens?

which compound can be used to preserve biological specimens?
Answer
Brief Explanations:
Formaldehyde (the first - shown compound which is an aldehyde) is commonly used to preserve biological specimens. It works by cross - linking proteins and other biological macromolecules, preventing decay. The other two compounds are esters and ketones and not used for specimen preservation.
Answer:
The first compound (aldehyde structure: $\text{HCHO}$)