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

Ex Input:
Which category contains a 2 year old tree?, Context: To accurately map the Amazon's biomass and subsequent carbon related emissions, the classification of tree growth stages within different parts of the forest is crucial. In 2006 Tatiana Kuplich organized the trees of the Amazon into four categories: (1) mature forest, (2) regenerating forest [less than three years], (3) regenerating forest [between three and five years of regrowth], and (4) regenerating forest [eleven to eighteen years of continued development]. The researcher used a combination of Synthetic aperture radar (SAR) and Thematic Mapper (TM) to accurately place the different portions of the Amazon into one of the four classifications.

Ex Output:
2


Ex Input:
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 Output:
exhaust and compression periods


Ex Input:
Does the fire apparatus fleet have more hazardous materials units or Technical Rescue Units?, Context: Oklahoma City is protected by the Oklahoma City Fire Department (OKCFD), which employs 1015 paid, professional firefighters. The current Chief of Department is G. Keith Bryant, the department is also commanded by three Deputy Chiefs, who – along with the department chief – oversee the Operational Services, Prevention Services, and Support Services bureaus. The OKCFD currently operates out of 37 fire stations, located throughout the city in six battalions. The OKCFD also operates a fire apparatus fleet of 36 engines (including 30 paramedic engines), 13 ladders, 16 brush patrol units, six water tankers, two hazardous materials units, one Technical Rescue Unit, one Air Supply Unit, six Arson Investigation Units, and one Rehabilitation Unit. Each engine is staffed with a driver, an officer, and one to two firefighters, while each ladder company is staffed with a driver, an officer, and one firefighter. Minimum staffing per shift is 213 personnel. The Oklahoma City Fire Department responds to over 70,000 emergency calls annually.

Ex Output:

hazardous materials units