It is implied in the passage that()

• A、all high-school students take the same courses

• B、every high-school student must take some practical ability training courses

• C、every public school offers the same academic subjects

• D、the subjects every student takes may vary

American Roads

The United Stares is. well-known for its network of major high ways designed to help a driver get from come place to another in the shortest possible time. Although these wide modern 31___ are generally smooth and well maintained. with few sharp CT and straight sections,a direct route is not always the most 32___ one. Large highways often piss by scenic areas and interesting small 33___Furthermore.these highways generally connect large urban centers,which 34___that they become crowded with heavy traffic during rush hours,when the "fast,direct" route becomes a very slow route,

However, there is almost always another route to take 35___ you are noting hurry.Not far from the 36___ news “superhighways" .there are often older.37___ heavily traveled roads which go through the countryside. Some of These are good two lane roads others are uneven roads curving through the country. These secondary routes may go 38___steep slopes, along high cliffs, or down frightening hillside to towns 39___in deep alleys. Through these less direct routes.longer and slower,they generally go to places 40___the air is clean and scenery is beautiful,and the driver may have a chance to get a fresh.clean view of the world.

A. Less

B. Up

C. Enjoyable

D. Relatively

E.means

F. Roads

G. lying

H. Through

I.which

J.if

K. where

L. towns

Sharks Perform a Service for Earth's Waters

It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to attack frequently. Although these fish perform a 41___ ( value) service for earth's waters and for human beings. business and sport fishing are 42___ (threat) their existence.As a result,some sharks are at risk of disappearing from Earth.

Warm weather may influence. both fish and shark 43___ (active). Many fish swim near coastal areas because of their warm waters. Experts say sharks may follow the fish into the same areas，where people also swim. In fact ,most sharks do not44___( purpose)charge at or bite humans. They are__ 45 ( think) to mistake a person for a sea animal,such as a sea (海豹) or sea lion, That is why people should not swim in the ocean when the sun.46___ (go) down or comes up. because those are the times when sharks are looking for food. Experts also say that bright colors and shiny jewelry(珠 宝) may cause sharks to attack.

Medical researchers want to learn 47___ (much) about the shark's body defense and immune(免疫的) systems against disease. 48__ ( research) know that sharks recover quickly from injuries. They study the shark in hope of finding a way to fight human disease.

Sharks are important for the world's oceans,as they eat 49___(injure). and diseased fish. Their 50__ ( hunt) activities mean that the numbers of other fish in ocean waters do not become too great.This protects the plants and other forms of life that exist in the oceans.