The state of the soil when plants fail to extract sufficient water for their requirements, is

Answer: Option B

The correct answer is Permanent wilting point.

In irrigation engineering, the term Permanent wilting point refers to the state of the soil when plants are unable to extract sufficient water for their needs. At this point, the soil moisture content is so low that plants wilt permanently, even if moisture is added to the soil.

So, the sentence should read: "The state of the soil when plants fail to extract sufficient water for their requirements, is Permanent wilting point."