Drones zoom around almost everywhere these days. Farmers use them to monitor crops. Scientists use them to study hostile places， such as the inside of a volcano. Others fly them as a hobby. But drones of the future may not look like todays models. But how well will such novel vehicles perform？ Engineers at the Massachusetts Institute of Technology， in Cambridge， have created a new computer program that lets users design their own flying machines — and then pretest them.

Many personal drones are some style of multicopter — a flying machine with spinning propellers. Quadcopters have four. Hexacopters have six. Yet “there are plenty of cases in which standard quadcopters and hexacopters might not be the best solution for a given task，” notes Tao Du. “There are only a small range of options for drones that you can buy，”points out this MIT graduate student who worked on the new program.

The system from Dus team is the ultimate in do-it-yourself. It lets people pick the size， shape and structure that best fits their needs. Such an approach increases the shapes， styles and sizes of drones that users can fly and what they can do with them. And the designers dont need to be experts in physics to do it.

Multicopters use their propellers to turn or go up and down. But the ones available to consumers cant fit every need. For example， a scientist who wants to attach a special camera may find that the drones propellers block its view. Or， a drone might need to carry an object with an irregular shape. Say， for instance， you want a drone to carry an egg. With an off-the-shelf model， youd have to rig up something that might destabilize it and cause it to crash. But if you design your own， you can build an egg carrier and choose a design that will keep it stable.

The MIT system could help in such situations. As they design a custom machine that actually flies， DIYers must consider a number of questions. What happens when many propellers spin at once？ How many parts can you add and still keep a drone lightweight enough to fly well？ How much propeller power does the machine need to overcome gravity？

1. Which of the following is similar in meaning to hostile in the underlined sentence？ ____.

A. deep B. unfavorable

C. untapped D. faraway

2. What is the major contribution by MIT engineers？ ____.

A. They have made a major breakthrough in making drones

B. They have designed a novel drone

C. They have created a computer system that can be used to produce standard drones

D. They have created a program enabling users to design drones for specific purposes

3. An off-the-shelf model in Paragraph 4 refers to ____.

A. a drone that can be customized for its size， shape and structure

B. a DIY system recently developed by MIT graduate students

C. a standard flying machine with spinning propellers

D. an egg carrier with customized designs to address the problem of irregular shape

4. Gravity in the last paragraph refers to ____.

A. a force that causes drones to turn or go up and down

B. a driving force provided by propellers

C. a powerful force caused by a volcano

D. a force that causes objects to fall or to be attracted to the groundendprint