Answer:
b. the second voice from the top, or alto
Step-by-step explanation:
Fugue, in general, is a polyphonic composition that introduces the subject of a melodic theme by a voice or a part, to then be taken and refined by others.
Bach's The Art of Fugue is considered to be a masterpiece of music, divided into seven groups. Contrapunctus I is one of the simple figures, and in it, four voices are introduced. First heard is the second-highest voice from the top also known as alto.