What is true about most higher-grade metallic ores? They are usually found deep below Earth’s surface—more than 1,000 ft underground.

Question

They are usually found deep below Earth’s surface—more than 1,000 ft underground.

Most of them can be extracted using the placer method.
Most of them can be extracted using the placer method.

Most of them can be extracted without requiring drilling.
Most of them can be extracted without requiring drilling.

They are usually found very close to Earth’s surface—less than 1,000 ft underground.
They are usually found very close to Earth’s surface—less than 1,000 ft underground.

Answer 1

The statement that is generally true about most higher-grade metallic ores is:

They are usually found deep below Earth’s surface—more than 1,000 ft underground.

Higher-grade metallic ores, which have a higher concentration of the desired metal, are often located deeper within the Earth's crust, requiring more extensive mining techniques that can involve drilling and excavation.

The other statements regarding the placer method and extraction without drilling are typically less applicable to higher-grade metallic ores. Placer mining is more associated with alluvial deposits of metals such as gold, where the ore can be found in sediment, and many underground ores do indeed require drilling for extraction.

Lastly, while some metallic ores can be found closer to the surface, higher-grade metallic ores are more commonly located at greater depths.