【判断题】When the views of a composite solid formed by adding are drawn, the solid can be c
This schematic makes sense if:
A、❶ is solid and ❸ is liquid
B、❶ is gas and ❸ is liquid
C、❶ is gas and ❸ is solid
D、❶ is liquid and ❸ is solid
Halley's Comet (慧星) completed its latest trip around the Earth in 1986. It is now speeding toward the far-distant edges of our solar system. People on Earth will not be able to see it again until 2062. Scientists in many countries waited and prepared for years for the return of Halley's Comet. They planned new ways to observe the comet as it came near the Earth. Comets are of great interest to scientists. This is because the space objects are believed to have changed very little since the solar system was formed 4,600 million years ago. Scientists believe that if they can learn more about the elements in a comet, they will understand more about conditions when the solar system was new. Halley's Comet is probably the most famous comet. Historians say it was first noted about 2,200 years ago. The visit of the bright space object has been observed and recorded every 76 years since then. The comet was named after British scientist Edmund Halley. In the early 1700s, Halley studied records of the appearance of huge balls of fire flying across the sky. And he studied the sky to make his own observations. Halley was the first person to recognize that the balls of fire were really the same bright object, a comet. Halley said the comet circled the sun just as the planets did. And he said the comet's trip around the sun took about 76 years. Since the discoveries by Edmund Halley, people have waited for that bright comet to return. When it came, people looked at it through small telescopes (望远镜) they held in their hands. And scientists looked at it through huge telescopes placed on top of mountains where the air was clear. But the most recent visit of Halley's Comet was the first time scientists could study the comet up very close. They did this through scientific instruments sent into space. 13. Scientists are interested in comets in that ________.
A、comets are bright space objects
B、people will not be able to see them until 2062
C、they believe that if they can learn more about the elements in a comet, they will understand more about solar system
D、the space objects are believed to have changed very little since the solar system was formed 4,600 million years ago
A. 1.5m B. 1.4m C. 1.3m
【判断题】From this figure, we can see that the horizontal projection and the profile projection of the intersection of the external cylindrical surface and the internal cylindrical surface are both in the circles in the top view and the left-side view.
A、Full sectional view
B、Half sectional view
C、Offset section
D、Broken-out section
【单选题】Which projection gives the true length of line AB?
A、Frontal projection
B、Horizontal projection
C、Profile projection
D、None of them
【判断题】In CATIA software, the command Padcan be used to extrude a sketch only along one direction.
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