【正确答案】 D

【答案解析】
[解题思路] 了解在上个世纪道路建设的材料。
[详细解答] The engineer回答是：Usually they were gravel and macadam．Tars and asphalt were originally used only as coverings，but later they were used as binders and finally as hot mixtures．“gravel”为“a loose mixture of rock fragments or pebbles”砾石；“macadam”为“pavement made of layers of compacted broken stone； now usd，bound with tar or asphalt”碎石。
[听力原文]<1>-<5>
Mr. Jones: What materials were used for road surfaces during the last century?
Engineer: Usually they were gravel and macadam. Tars and asphalt were originally used only as coverings, but later they were used as binders and finally as hot mixtures.
Mr. Jones: Concrete is a modern material as far as road - building goes, isn't it?
Engineer: Relatively speaking. But you might be surprised to know that a concrete road was built as early as 1893 in Ohio. But it was only 5 miles long. More extensive projects were not undertaken until much later, around 1912 or 1913.
Mr. Jones: This was because of the increase in traffic?
Engineer: That's right. Especially in the use of heavy tracks. More rigid pavements, such as concrete and brick, became a necessity. For light traffic, though, water-bound macadam, gravel, sand clay, and bituminous mixtures were still used.
Mr. Jones: What are turnpikes usually made of?
Engineer: Turnpikes are usually made of reinforced concrete about 8 to 10 inches thick, placed on a granular sub-base, which in turn is placed on a well - tacked earth subgrade. Of course, the construction depends a lot on the local climate, rainfall, soils, and so on.
Mr. Jones: How do you mean--climate?
Engineer: Frost is one of the main problems. For example, in Maine, where frost is quite frequent, the typical turnpike construction is a thin top layer of asphaltic concrete on a base layer of sand and gravel placed on a 36 - inch, frost - free, granular sub - grade.
Mr. Jones: What is the width of these roads?
Engineer: The early two - lane roads were about 20 feet wide. But with higher automobile speeds, the width requirements increased greatly. To give you an example, the Pennsylvania Turnpike has two 12 - foot lanes in each direction, separated by a median 10 feet wide. On each side there is a 10 - foot stabilized shoulder, marking a total width of 78 feet. The New Jersey Turnpike averages 100 feet in width, with three lanes in each direction.
Mr. Jones: I guess wider roads are being built every day.
Engrneer: That's right. Sometimes you think that, no matter how good a road you build, the speed and weight of vehicles will always be one step ahead.

【正确答案】 A

【答案解析】[解题思路] 了解混凝土用于长距离工程的原因。 [详细解答] “concrete”为“a constraction material consisting of sand，conglomerate gravel，broken stone，or slag in a mortar or cement matrix”混泥土。

【正确答案】 C

【答案解析】[解题思路] 了解交通量大小的差异。 [详细解答] The engineer指出：For light traffic，water- bound macadam，gravel，sand clay，and bituminous mixtures are used．“bituminous”为“like or containing any of various flammable mixtures of hydrocarbons and other substances that are constituents of asphalt and tar．”含有沥青的。

【正确答案】 D

【答案解析】[解题思路] 了解“turnpike”的含义。 [详细解答] 这个题可以用排除法。Roads，streets， lanes are not heavy surfaces．只有turnpikes are extensive surfaces．高速公路。

【正确答案】 B

【答案解析】[解题思路] 了解宾夕法尼亚高速公路的整个宽度。 [详细解答] 宾州高速公路每一个方向为12英尺，中间被10英尺的路面隔开，每一边又拓宽10英尺，这样总宽度为78英尺。