Below are the choices that can be found from other sources:
Robertsonian translocation
Pericentric inversion
Unbalanced translocation
Reciprocal balanced translocation
The answer is Robertsonian translocation. Robertsonian translocation (ROB) is a rare form of chromosomal rearrangement that, in humans, occurs in the five acrocentric chromosome pairs, namely 13, 14, 15, 21 and 22. Other translocations occur but do not lead to a viable fetus.