Answer: A — Pb (Lead)
Lead (Pb) is a poor conductor of electricity compared to Cu (copper), Ag (silver), and Al (aluminium), which are all good conductors.
Cu, Ag, and Al are metals widely used as electrical conductors (Ag is the best conductor, Cu and Al are used in wiring). Lead (Pb) is a metal but has significantly higher resistivity, making it a poor conductor relative to the others. The textbook mentions Al, Cu as fuse/wire materials for good conductivity; Pb is notably absent from such applications.