ANS:D - boron

Silicon crystal can be converted to p-type semiconductor by doping it with boron. In semiconductor physics, doping refers to the intentional introduction of impurities into a semiconductor crystal to modify its electrical properties. Boron is a group III element in the periodic table, which means it has three valence electrons. When boron is added as a dopant to a silicon crystal (which has four valence electrons), it creates a p-type semiconductor. Here's how the process works:

• Boron atoms replace some of the silicon atoms in the crystal lattice.
• Since boron has one fewer electron than silicon, it creates a "hole" in the crystal lattice, effectively creating a positive charge carrier.
• These "holes" act as positive charge carriers, allowing them to move through the crystal when an electric field is applied.