What are the shading techniques called?

Its true

The correct answer is a.the castrati were classical singers with very high voice equivalent to that of a soprano, mezzo-soprano or contralto. this effect of high voice was produced by castration before puberty or an endocrinological condition. the castrati first started signing at the church but then they also sang at the opera. they did not only sang in italy but in many churches in europe. finally, they were singing male and female roles as well.