In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

[Q]: How can you reduce the jnd?, Context: The just-noticeable difference (jnd) (the threshold at which a change is perceived) depends on the tone's frequency content. Below 500 Hz, the jnd is about 3 Hz for sine waves, and 1 Hz for complex tones; above 1000 Hz, the jnd for sine waves is about 0.6% (about 10 cents). The jnd is typically tested by playing two tones in quick succession with the listener asked if there was a difference in their pitches. The jnd becomes smaller if the two tones are played simultaneously as the listener is then able to discern beat frequencies. The total number of perceptible pitch steps in the range of human hearing is about 1,400; the total number of notes in the equal-tempered scale, from 16 to 16,000 Hz, is 120.
[A]: two tones are played simultaneously


[Q]: What could have been a threat to the signatures being obtained?, Context: Despite the disagreements on the Eucharist, the Marburg Colloquy paved the way for the signing in 1530 of the Augsburg Confession, and for the formation of the Schmalkaldic League the following year by leading Protestant nobles such as John of Saxony, Philip of Hesse, and George, Margrave of Brandenburg-Ansbach. The Swiss cities, however, did not sign these agreements.
[A]: disagreements on the Eucharist


[Q]: What could you buy at Badagry?, Context: For centuries, various peoples in modern-day Nigeria traded overland with traders from North Africa. Cities in the area became regional centres in a broad network of trade routes that spanned western, central and northern Africa. In the 16th century, Spanish and Portuguese explorers were the first Europeans to begin significant, direct trade with peoples of modern-day Nigeria, at the port they named Lagos and in Calabar. Europeans traded goods with peoples at the coast; coastal trade with Europeans also marked the beginnings of the Atlantic slave trade. The port of Calabar on the historical Bight of Biafra (now commonly referred to as the Bight of Bonny) become one of the largest slave trading posts in West Africa in the era of the transatlantic slave trade. Other major slaving ports in Nigeria were located in Badagry, Lagos on the Bight of Benin and on Bonny Island on the Bight of Biafra. The majority of those enslaved and taken to these ports were captured in raids and wars. Usually the captives were taken back to the conquerors' territory as forced labour; after time, they were sometimes acculturated and absorbed into the conquerors' society. A number of slave routes were established throughout Nigeria linking the hinterland areas with the major coastal ports. Some of the more prolific slave traders were linked with the Oyo Empire in the southwest, the Aro Confederacy in the southeast and the Sokoto Caliphate in the north.
[A]:
slave