Final answer:
The unidentified mineral is most likely quartz due to its clear appearance, conchoidal fracture, and ability to scratch glass.
Step-by-step explanation:
Based on the given information, the unidentified mineral that is clear, exhibits conchoidal fracture, and can scratch glass is most likely quartz (option b).
Quartz is one of the most common minerals in the Earth's crust and has a non-metallic luster. It is known for its six-sided crystal form and its ability to scratch glass due to its hardness.
Additionally, the characteristic of conchoidal fracture, which means the mineral breaks into smooth, curved surfaces resembling the inside of a seashell, further supports the identification of the mineral as quartz.