Identify the relationship in each of the following pairs. Do the drawings represent constitutional isomers or stereoisomers,

Question:

Identify the relationship in each of the following pairs. Do the drawings represent constitutional isomers or stereoisomers, or are they just different ways of drawing the same compound? If they are stereoisomers, are they enantiomers or diastereomers? (Molecular models may prove useful in this problem.)