Which of the following types of boundaries is most likely to result in a subduction zone?
a. divergent
b. convergent
c. transform
d. all of the above

The answer is B. (convergent boundaries)

  The subduction zone is the place where two lithospheric plates come together, one riding  over the other.  

Subduction is said to be the process that takes place at convergent boundaries, by which one tectonic plate moves under another tectonic plate and sinks into the mantle as the plates converge. Regions where this process takes place are known as subduction zones.

As far as studies have shown, Earth is the only planet where subduction is known to occur.   

B, it's when the plate boundary merge together which is convergent boundary.