Which of the following is an example of metalloid?

The correct answer is option 3. Boron.

An example of a metalloid among the options provided is Boron.

Boron is a metalloid element that exhibits properties intermediate between those of metals and nonmetals. It is located in Group 13 of the periodic table and is commonly classified as a metalloid due to its mixed metallic and nonmetallic properties. Boron is used in various applications, including as a component in ceramics, semiconductors, and borosilicate glass.