Which, If Any, of the Following Descriptions Is False

Short Answer

Which, if any, of the following descriptions is false?
Uniparental disomy
a) means that in a diploid cell two copies of the same chromosome are inherited from one parent.
b) is very rare.
c) can be the outcome of a trisomic zygote that is unstable and ejects a chromosome from one parent, but keeps two copies of the same chromosome from the other parent.
d) can occur when a sperm fertilizes an egg that lacks one chromosome, and the resulting unstable zygote is able to recover by duplicating the single chromosome.