Which statement describes a property that is unique to metalloids?

• A. They react vigorously with water to produce hydrogen gas.
• B. They can act as semiconductors under certain conditions.
• C. They are always good conductors of electricity.
• D. They are completely nonreactive and do not form compounds.

Answer: (B)

Verified step by step guidance

1. Understand the classification of elements: metals, nonmetals, and metalloids. Metalloids have properties intermediate between metals and nonmetals.
2. Recall that metals typically react vigorously with water to produce hydrogen gas, so this property is not unique to metalloids.
3. Recognize that good electrical conductivity is a characteristic of metals, not metalloids, so metalloids are not always good conductors.
4. Note that being completely nonreactive and not forming compounds is a property of noble gases, not metalloids.
5. Identify that metalloids can act as semiconductors under certain conditions, which is a unique and defining property distinguishing them from metals and nonmetals.