The odd one out is B. Silicon.
The other three elements, A. Potassium, C. Zirconium, and D. Gallium, are all metals. Silicon is a metalloid.
A metalloid is a chemical element that has properties that are intermediate between those of metals and nonmetals. Metalloids are typically semiconductors, meaning that they conduct electricity better than nonmetals but not as well as metals.
Potassium is a soft, silvery-white metal that is highly reactive. It is the 19th most abundant element in the Earth’s crust and is found in many minerals, including sylvite, carnallite, and kainite. Potassium is used in a variety of applications, including fertilizers, batteries, and explosives.
Zirconium is a hard, white metal that is resistant to corrosion. It is the 40th most abundant element in the Earth’s crust and is found in many minerals, including zircon, baddeleyite, and gahnite. Zirconium is used in a variety of applications, including nuclear reactors, jet engines, and jewelry.
Gallium is a soft, silvery-white metal that melts at a very low temperature. It is the 31st most abundant element in the Earth’s crust and is found in many minerals, including bauxite, gallite, and sphalerite. Gallium is used in a variety of applications, including semiconductors, lasers, and solar cells.