Microorganisms require moisture to grow, which is measured in the form of–

Correct option is C

Option (a): Incorrect
• Dry basis moisture expresses percentage of water relative to dry solids but does not indicate microbial availability of water.
Option (b): Incorrect
• Wet basis moisture shows total water percentage in the product, not the biologically available water needed for microbial growth.
Option (c): Correct
• Water Activity (aw) measures the available moisture for microbial growth, not total moisture.
• Most bacteria require aw > 0.90; molds can grow at lower levels.
Option (d): Incorrect
• Absolute value does not represent usable water for microbes.