Final answer:
The compound with an electron group geometry and molecular geometry both described as linear would have a linear molecular geometry, such as CO2.
Step-by-step explanation:
A molecule will have a linear molecular geometry if its central atom is bonded to two other atoms with no lone pairs present, or it contains only two atoms. This spatial arrangement occurs because the electron groups are oriented 180° apart to minimize repulsions, leading to a linear shape. One example provided is CO2, where carbon is the central atom double-bonded to two oxygen atoms, all lying in a straight line.
From the provided options, the compounds with electron group geometry: linear and molecular geometry: linear would have a linear molecular geometry. Therefore, according to option 5a, a molecule with a linear electron group geometry and a linear molecular geometry fits the description and would exhibit a linear shape.