The correct relationship between the following structures is that they are

Concept: -

• Isomerism is the name given to a phenomenon in which more than one compounds have the same chemical formula but a different chemical structure. Compounds having the same molecular formula but different arrangements of atoms are called isomers.
• In isomerism, the chemical formula of compounds is the same but their arrangement is different.
• As the name suggests functional isomers are isomers that have the same chemical formula but the functional group present in the compound is different. 
• Structural isomers are divided into chain, positional, functional, metamerism, tautomerism, and ring chain isomers.
• Structural isomerism is commonly called constitutional isomerism.
  • In these isomers, functional groups and atoms in the molecules are connected in different ways.

• Stereoisomers: 
  • The compounds having the same molecular as well as the same structural formulae but differing in the relative arrangement of the atoms or groups in space are called stereoisomers.
  • This phenomenon is termed as stereoisomerism. 
  • Optically Active Stereoisomers: The stereoisomers that can rotate plane-polarized light are called as optically active whereas an optically inactive compound is not capable of optical rotation.
• Diastereomers:
  • Stereoisomers that are not mirror images of each other.
  • Diastereomers have the same configuration at least at one chiral centre and the opposite configuration at the remaining chiral centres.
• Enantiomers:
  • Stereoisomers are mirror images of each other.
  • Enantiomers have opposite configurations at all the chiral centres.

Explanation: 

• As we can see from the structure the linkage of atoms is the same in both thus, it rules out the possibility of constitution isomerism.
• Let's draw a mirror between two structures given to check whether they are mirror images of each other or not -
   

• As we can see both are mirror images of each other.
• Now, let's check whether they are superimposable or not -

• Thus, both structures as identical.

Conclusion: -

Both structures are superimposable mirror images of each other

Thus, they are identical.

Hence, the correct option is (1).

Alternate Method

• Check the symmetry elements of the structure.
• We can see that structure has a two-fold improper axis of symmetry.
• Thus, is optically inactive.
• We know the rotation of 180º in the plane of paper of a structure does not bring any change in configuration.
• Hence, both are homomers or identical.