Question

An igneous rock with small, barely discernible crystals most likely formed

a. deep within the earth

b. from a lava flow

c. below Earth's surface, near a volcano

Answer 1

b small crystals could come from very rapid cooling of molten rock/lava from a volcano. Process sometimes called "quenching". If the melt is cooled more "slowly" any crystals that form can grow into bigger crystals.
The words "slow" and big and small are more descriptive than actually "readings on a clock", or measurements with a metre rule.

Answer 2

B