Answer:

1. a compound with a linear structure

2. an arrangement of atoms of the same type that forms a ring

3. alkenes

Explanation:

explanation on number three, unsaturated hydrocarbons that contain one or more double bonds are called alkenes.

explanation on number two, aromatic rings are hydrocarbons which contain benzene,

explanation on number 1,  a compound with linear structure are the linear molecular geometry describes the geometry around a central atom bonded to two other atoms

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