Question

isomers: may occur in several different forms. may have vastly different physical properties. have the same chemical formula. all of the above. differ in their 3 - d chemical structure.

Explanation:

Isomers are compounds with the same chemical formula but different structures. They can exist in multiple forms (like structural isomers, stereoisomers etc.). Due to different structures, they can have different physical properties (e.g., boiling point, melting point). And they do differ in 3 - D chemical structure (in case of stereoisomers like cis - trans isomers or in structural isomers in terms of connectivity which also has a 3 - D aspect).

Answer:

all of the above.