The energy band diagrams for three semiconductor samples of silicon are as shown. We can then assert that

sample X is undoped, while samples Y and Z have been doped with a fifth group and a third group impurity, respectively.

sample X is undoped, while samples Y and Z have been doped with a third group and a fifth group impurity, respectively.

sample X has been doped with equal amounts of third and fifth group impurities, while samples Y and Z are undoped.

sample X is undoped, while both samples y and Z have been doped with a fifth group impurity.