What is it called when stride pianists take turns trying to outplay one another in speed and technique?

In the middle section of "My Lord Help Me to Pray," the voices overlap to create a __________

a) slow homophonic texture b) texture of pervading imitation c) monophonic chant-like texture d) thick polyphonic texture

A ________ is a short drum pattern that a DJ creates and repeats over and over.

Fill in the blank(s) with the appropriate word(s).