Which of the following best describes a semiconductor?

A semiconductor is indeed best described as a material that can manipulate electrical conductivity. This means that it can either conduct electricity or act as an insulator depending on various factors such as temperature, doping (adding impurities), and the presence of an electric field. Semiconductors typically have conductivity levels that lie between those of insulators and conductors, which allows them to be very useful in electronic devices. For example, silicon, a common semiconductor, can be altered through doping to enhance its conductivity, enabling it to function effectively in diodes, transistors, and integrated circuits. This unique ability to adjust its conductive properties is what makes semiconductors crucial for modern electronics.