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

[EX Q]: How does a chestnut tree form its heartwood?, Context: The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. Others never form heartwood.
[EX A]: the change comes slowly

[EX Q]: What was Cork City formerly surrounded by?, Context: The city's charter was granted by Prince John, as Lord of Ireland, in 1185. The city was once fully walled, and some wall sections and gates remain today. For much of the Middle Ages, Cork city was an outpost of Old English culture in the midst of a predominantly hostile Gaelic countryside and cut off from the English government in the Pale around Dublin. Neighbouring Gaelic and Hiberno-Norman lords extorted "Black Rent" from the citizens to keep them from attacking the city. The present extent of the city has exceeded the medieval boundaries of the Barony of Cork City; it now takes in much of the neighbouring Barony of Cork. Together, these baronies are located between the Barony of Barrymore to the east, Muskerry East to the west and Kerrycurrihy to the south.
[EX A]: wall

[EX Q]: Were there more troops in the right column or in the centre column?, Context: Accordingly, leaving Field Marshal Count Kurt von Schwerin in Silesia with 25,000 soldiers to guard against incursions from Moravia or Hungary, and leaving Field Marshal Hans von Lehwaldt in East Prussia to guard against Russian invasion from the east, Frederick set off with his army for Saxony. The Prussian army marched in three columns. On the right was a column of about 15,000 men under the command of Prince Ferdinand of Brunswick. On the left was a column of 18,000 men under the command of the Duke of Brunswick-Bevern. In the centre was Frederick II, himself with Field Marshal James Keith commanding a corps of 30,000 troops. Ferdinand of Brunswick was to close in on the town of Chemnitz. The Duke of Brunswick-Bevern was to traverse Lusatia to close in on Bautzen. Meanwhile, Frederick and Field Marshal Keith would make for Dresden.
[EX A]:
centre