The correct option is (b) a p-type semiconductor.
Explanation:
Arr intrinsic germanium have four outer electrons which they use to form bonds with four neighbouring Ge atoms. Gallium, being from group III is having three outer electrons. So when we add gallium atoms into germanium, some gallium atoms have a chance to replace some of the germanium atoms. But with gallium, only three neighbouring Ge atoms can make bonds with Ga. The bond with the fourth neighbouring Ge atom is broken as Ga is having a shortage of one outer electron. The broken bond can be filled up by an electron when the electron gets enough energy to jump from the valance bond creating a hole out there. So, we get a p -type semiconductor.
