instruction:
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
question:
What needs consistency?, Context: The simplest valve gears give events of fixed length during the engine cycle and often make the engine rotate in only one direction. Most however have a reversing mechanism which additionally can provide means for saving steam as speed and momentum are gained by gradually "shortening the cutoff" or rather, shortening the admission event; this in turn proportionately lengthens the expansion period. However, as one and the same valve usually controls both steam flows, a short cutoff at admission adversely affects the exhaust and compression periods which should ideally always be kept fairly constant; if the exhaust event is too brief, the totality of the exhaust steam cannot evacuate the cylinder, choking it and giving excessive compression ("kick back").[citation needed]
answer:
exhaust and compression periods


question:
Why was the country growing problematic?, Context: With Burma preoccupied by the Chinese threat, Ayutthaya recovered its territories by 1770, and went on to capture Lan Na by 1776. Burma and Siam went to war until 1855, but all resulted in a stalemate, exchanging Tenasserim (to Burma) and Lan Na (to Ayutthaya). Faced with a powerful China and a resurgent Ayutthaya in the east, King Bodawpaya turned west, acquiring Arakan (1785), Manipur (1814) and Assam (1817). It was the second-largest empire in Burmese history but also one with a long ill-defined border with British India.
answer:
one with a long ill-defined border with British India


question:
The abbey bells were downsized to what number?, Context: The bells at the abbey were overhauled in 1971. The ring is now made up of ten bells, hung for change ringing, cast in 1971, by the Whitechapel Bell Foundry, tuned to the notes: F#, E, D, C#, B, A, G, F#, E and D. The Tenor bell in D (588.5 Hz) has a weight of 30 cwt, 1 qtr, 15 lb (3403 lb or 1544 kg).
answer:

ten bells