What is the term used to refer to oral poets in many parts of Africa (such as Sierra Leone)?

In terms of harmony, "Knee Play 1" __________

a) shifts dramatically among far-removed key areas b) is atonal, avoiding any key center c) follows a simple harmonic progression based on only three chords d) uses a ritornello structure

What are the characteristics of de Stijl and how do Piet Mondrian's Composition with Yellow, Red, and Blue and Gerrit Rietveld's Schroder House embody the movement?

What will be an ideal response?