单选题The crankshafts on the large modern 2-stroke crosshead engines are （）big （）makes as a single unit and so are constructed by joining together individual forgings.A enough；toB too；toC such；soD so；that

Large crosshead type engine generally has two lubrication systems, a function performed only by crankcase oil system is（）

The main function of tie rods in the construction of large, low speed diesel engines is to（）.

The guide shoes are secured to the crosshead by means of（）

Oxford　　When language learners arrive in Oxford, many ask where the university is, thinking that they will be shown just one building. It’s up to their teachers to explain that Oxford university is made up of a collection of many different colleges and institutions, each with its own history and characteristics.　　There are many other surprises that learners discover about the city and its university. Katie Jennings is a social organizer at King’s St Joseph’s Hall in East Oxford, and it is her job to organize activities for learners outside of lesson time. She says many learners are surprised to discover that Oxford is a home to a wide variety of nationalities and ethnic groups, and one of the most popular social events is a night out at one of the town’s Latin American dance clubs. After a day spent learning English and absorbing the ancient atmosphere of the university, learners can samba the night away.　　The city also has a thriving Asian community, and the sight of women in saris is as common in Oxford’s streets as academics in gowns and mortarboards. There is also a mouth-watering selection of Asian restaurants serving curries, as well as shops stocked with exotic vegetables and fruits.　　The city has attracted such a diverse population not only because of the university, but also because it is an important industrial centre which is known for car manufacturing among other things. In spite of large industrial areas, the old of the city centre has remained surprisingly intact.　　Carmel Engin, who teaches at the Lake School, says many learners are surprised to find that the city is free from the usual high-rise modern buildings. “From the centre of Oxford, you can see green hills in the distance, and this will make learners deeply feel that they are in a small, friendly town, but not just another modern metropolis.”　　Some learners will be tempted to explore those green hills—Oxford is surrounded by some of the most beautiful countryside in southern England—but, as Engin admits, with so much to do and see in the city, few learners find the time, to explore its surroundings.

（） can be found on most medium to large merchant vessels even if the main engine is either a steam turbine or 2-stroke crosshead engine.

Large marine diesel engines of crosshead construction generally have two systems of lubrication: a total loss system feeding the （） and a recirculation system lubricating the running gear and cooling the piston.

On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.