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

[Q]: 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]
[A]: exhaust and compression periods


[Q]: The most heat-treatable alloys are decided but only?, Context: Conversely, most heat-treatable alloys are precipitation hardening alloys, which produce the opposite effects that steel does. When heated to form a solution and then cooled quickly, these alloys become much softer than normal, during the diffusionless transformation, and then harden as they age. The solutes in these alloys will precipitate over time, forming intermetallic phases, which are difficult to discern from the base metal. Unlike steel, in which the solid solution separates to form different crystal phases, precipitation hardening alloys separate to form different phases within the same crystal. These intermetallic alloys appear homogeneous in crystal structure, but tend to behave heterogeneous, becoming hard and somewhat brittle.
[A]: Conversely


[Q]: Where can the news in Oklahoma be read in print every seven days?, Context: The Oklahoman is Oklahoma City's major daily newspaper and is the most widely circulated in the state. NewsOK.com is the Oklahoman's online presence. Oklahoma Gazette is Oklahoma City's independent newsweekly, featuring such staples as local commentary, feature stories, restaurant reviews and movie listings and music and entertainment. The Journal Record is the city's daily business newspaper and okcBIZ is a monthly publication that covers business news affecting those who live and work in Central Oklahoma.
[A]:
Oklahoma Gazette