- If something is a stage in a process then that something is required for that process
- The formation of metamorphic rock is a sequential process, with stages of rock being compacted, heated, recrystallized
- So, recrystallization is required for the process of the formation of metamorphic rock

- Recrystallization is a kind of event
- If an event is required for a process then that event must occur before that process can occur
- Hence, if recrystallization is required for a process then recrystalization must occur before that process can occur

- Recrystallization is required for the process of the formation of metamorphic rock
- If recrystallization is required for a process then recrystalization must occur before that process can occur
- So, recrystallization must occur for the formation of metamorphic rock to occur

- If something changes to something else then that something else is formed from that something
- Exposure to extreme heat and pressure changes / metamorphoses sedimentary / igneous rock into metamorphic rock
- So, metamorphic rock is formed from sedimentary rock

- Metamorphic rock is formed from sedimentary rock
- Sedimentary rock is made of sediment
- Hence, metamorphic rock is formed from sediment

- Recrystallization must occur for the formation of metamorphic rock to occur
- Metamorphic rock is formed from sediment
- Therefore, recrystallization must occur for sediments to form metamorphic rock

- Recrystallization must occur for sediments to form metamorphic rock
- Formation in the rock cycle means an old class of rocks changes into a new class of rocks
- Hence, recrystallization must occur for sediments to form a new rock

So, recrystallization must occur for sediments to form a new rock
Question
Which of these must occur for sediments to form new rock?

Context
- If something is a stage in a process then that something is required for that process 
- Sedimentary rock is made of sediment 
- If something changes to something else then that something else is formed from that something 
- Exposure to extreme heat and pressure changes / metamorphoses sedimentary / igneous rock into metamorphic rock 
- The formation of metamorphic rock is a sequential process, with stages of rock being compacted, heated, recrystallized 
- Recrystallization is a kind of event 
- If an event is required for a process then that event must occur before that process can occur 
- Formation in the rock cycle means an old class of rocks changes into a new class of rocks