Problem: Bird migration:

The primary physiological cue for migration are the changes in the day length. These changes are also related to hormonal changes in the birds. In the period before migration, many birds display higher activity or Zugunruhe (German: migratory restlessness), first described by Johann Friedrich Naumann in 1795, as well as physiological changes such as increased fat deposition. The occurrence of Zugunruhe even in cage-raised birds with no environmental cues (e.g. shortening of day and falling temperature) has pointed to the role of circannual endogenous programs in controlling bird migrations. Caged birds display a preferential flight direction that corresponds with the migratory direction they would take in nature, changing their preferential direction at roughly the same time their wild conspecifics change course.

What is the primary cue for migration?
---
A: changes in the day length


Problem: Electric motor:

All the electromagnetic motors, and that includes the types mentioned here derive the torque from the vector product of the interacting fields. For calculating the torque it is necessary to know the fields in the air gap . Once these have been established by mathematical analysis using FEA or other tools the torque may be calculated as the integral of all the vectors of force multiplied by the radius of each vector. The current flowing in the winding is producing the fields and for a motor using a magnetic material the field is not linearly proportional to the current. This makes the calculation difficult but a computer can do the many calculations needed.

 How are the very few calculations to determine torque done?
---
A: unanswerable


Problem: Guinea-Bissau:

Guinea-Bissau was once part of the kingdom of Gabu, part of the Mali Empire; parts of this kingdom persisted until the 18th century. Other parts of the territory in the current country were considered by the Portuguese as part of their empire. Portuguese Guinea was known as the Slave Coast, as it was a major area for the exportation of African slaves by Europeans to the western hemisphere. Previously slaves had been traded by Arabs north to the northern part of Africa and into the Middle East.

What area was known as the Slave Coast?
---
A: Portuguese Guinea


Problem: Military history of the United States:

Ongoing political tensions between Great Britain and the thirteen colonies reached a crisis in 1774 when the British placed the province of Massachusetts under martial law after the Patriots protested taxes they regarded as a violation of their constitutional rights as Englishmen. When shooting began at Lexington and Concord in April 1775, militia units from across New England rushed to Boston and bottled up the British in the city. The Continental Congress appointed George Washington as commander-in-chief of the newly created Continental Army, which was augmented throughout the war by colonial militia. He drove the British out of Boston but in late summer 1776 they returned to New York and nearly captured Washington's army. Meanwhile, the revolutionaries expelled British officials from the 13 states, and declared themselves an independent nation on July 4, 1776.

 What were the second conflicts of the American Revolution?
---
A:
unanswerable