The correct answer is C. Semiconductors.
A bus is a data transmission line that allows multiple devices to share a common communication path. A control unit is a component of a computer that is responsible for controlling the execution of instructions.
Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. They are used in a wide variety of electronic devices, including chips.
Option A is incorrect because buses are not used for manufacturing chips. Option B is incorrect because control units are not used for manufacturing chips. Option D is incorrect because buses and control units are not the only things used for manufacturing chips. Option E is incorrect because semiconductors are used for manufacturing chips.