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

[EX Q]: How bad were Nasser's heart attacks?, Context: Nasser had few personal vices other than chain smoking. He maintained 18-hour workdays and rarely took time off for vacations. The combination of smoking and working long hours contributed to his poor health. He was diagnosed with diabetes in the early 1960s and by the time of his death in 1970, he also had arteriosclerosis, heart disease, and high blood pressure. He suffered two major heart attacks (in 1966 and 1969), and was on bed rest for six weeks after the second episode. State media reported that Nasser's absence from the public view at that time was a result of influenza.
[EX A]: major heart attacks

[EX Q]: What part of the vegetation is measured?, Context: Oxygen presents two spectrophotometric absorption bands peaking at the wavelengths 687 and 760 nm. Some remote sensing scientists have proposed using the measurement of the radiance coming from vegetation canopies in those bands to characterize plant health status from a satellite platform. This approach exploits the fact that in those bands it is possible to discriminate the vegetation's reflectance from its fluorescence, which is much weaker. The measurement is technically difficult owing to the low signal-to-noise ratio and the physical structure of vegetation; but it has been proposed as a possible method of monitoring the carbon cycle from satellites on a global scale.
[EX A]:
canopies

