A semiconductor _____.

is a special material that conducts current like a regular conductor
is an insulating material through which a little current flows
conducts current only under certain conditions
conducts current better than a regular conductor

A semiconductor conducts current only under certain conditions. Its conductivity can be controlled by factors such as temperature, impurities, and electric fields. They are used in a variety of electronic devices such as transistors, diodes, and solar cells.