This is what is normally termed a single replacement reaction, although don't hold me to that. It could have changed to something more modern.
The given substance is SOLID. Solids have definite shape and definite volume. By the term definite we mean that wherever it may be placed both shape and volume remain the same. From the given above, the substance has a definite shape of sphere and definite volume of 50 mL.
Answer:
Miles (mi) or kilometers (km)
Explanation:
This is a big distance and it needs to be measured using a large unit of measurement, unlike feet, yards, or meters.