Salt concentration of ______ percent is sufficient to preserve most products.

Correct option is B

A salt concentration of 15-25% is generally sufficient to preserve most food products.
This concentration creates an environment that inhibits the growth of spoilage microorganisms by drawing water out of the cells through osmosis.
Other option:
· Option D: 35-45: This is a very high salt concentration and is typically used for preserving specific products like certain types of fish.