[单项选择]Most air conditioning units have （） for adjusting the ratio of recirculated fresh airCare must be taken not to reduce the fresh air so that stuffiness or smells arise.
A. catch plates
B. dampers
C. regulating valves
D. fans

[单项选择]The most serious effect of air trapped in a diesel engine jacket water cooling system is that it（）.
A. causes colloid suspension in the cooling water
B. reduces the capability of the lubrication system
C. can form pockets which block the flow of coolant through the system
D. leads to the scuffing of cylinder walls

[单项选择]

Most people have no idea of the hard work and worry that gointothe collecting of those fascinating birds and animals that they pay to see in the zoo.One of the questions that is always asked of me is 1 I became an animal collector in the first 2.The answer is that I have always been interested in animals and zoos.According to my parents, the first word I was able to say with any 3 was not the conventional “mamma” or “daddy”,4 the word “zoo”, which I would 5 over and over again with a shrill 6 until someone, ingroupsto 7 me up, would take me to the zoo.When I 8 a little older, we lived in Greece and I had a great 9 of pets, ranging from owls to seahorses, and I spent all my spare time 10 the countryside in search of fresh specimens to 11 to my collection of pets.12 on I went for a year to the City Zoo, as a student 13 , to get experience of the large animals, such as lions, bears, bison and ostriches,14 were not easy to keep at home.When I left, I 15 had enough money of my own to
A. clarity
B. emotion
C. sentiment
D. affection