Câu hỏi:
26/04/2022 564Sách mới 2k7: 30 đề đánh giá năng lực DHQG Hà Nội, Tp. Hồ Chí Minh, BKHN 2025 mới nhất (600 trang - chỉ từ 140k).
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Trả lời:
Đáp án A
Điều nào sau đây có thể được suy ra từ đoạn văn?
A. Stronti được phát hiện ủng hộ ý tưởng rằng sự hợp nhất sao neutron tạo ra nhiều yếu tố nặng hơn hơn sắt
B. Các nhà khoa học đã phát hiện ra một nguyên tố mới cho bảng tuần hoàn sau hậu quả của một va chạm của ngôi sao neutron
C. Một môi trường giàu neutron tạo ra các nguyên tố quá trình R nhẹ hơn so với môi trường không có neutron
D. Một cặp lỗ đen có năng suất cao hơn so với các sao neutron trong việc tạo ra vàng
Căn cứ vào thông tin đoạn hai:
Scientists had assumed that a collision by two super-dense objects, such as neutron stars, would trigger a chain of nuclear reactions. They're known as the r-process. … About half of all elements heavier than iron were thought to be made in the r-process. (Các nhà khoa học đã cho rằng một vụ va chạm giữa hai vật thể siêu dày đặc, như sao neutron, sẽ kích hoạt một chuỗi các phản ứng hạt nhân. Chúng được gọi là quá trình R… Khoảng một nửa trong số các nguyên tố nặng hơn sắt được cho là sẽ được tạo ra trong quá trình R.)
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Mark the letter A, B, C, or D to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions.
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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Astronomers have for the first time definitively ID’d the birth of a specific heavy element during a neutron-star smashup. They found strontium. And it showed up in the wavelengths of light — or spectra — making up this collision’s afterglow.
Scientists had assumed that a collision by two super-dense objects, such as neutron stars, would trigger a chain of nuclear reactions. They’re known as the r-process. In such an environment, the nuclei of atoms could rapidly gobble up neutrons. Afterward, those nuclei would become transformed in a process known as radioactive decay. The r-process was seen as a way to transform old, smaller elements into newer, bigger ones. About half of all elements heavier than iron were thought to be made in the r-process. Finding strontium in the recent collision at last offered the most direct evidence yet that neutron-star collisions really do trigger the r-process.
Physicists had long predicted that silver, gold and many other elements more massive than iron formed this way. But scientists weren’t sure where those r-process reactions took place. After all, no one had directly seen the r-process underway in a celestial event. Or they didn’t until the merger of two neutron stars in 2017. Scientists quickly analyzed light given off by that cataclysm. In it, they found evidence of the birth of a hodgepodge of heavy elements. All would seem to have come from the r-process.
The researchers were examining mostly very heavy elements — ones whose complex atomic structures can generate millions of spectral features. And all of those features were not yet fully known, Watson points out. This made it extremely difficult to tease apart which elements were present, he says.
Strontium, however, is relatively light compared to other r-process elements. And its simple atomic structure creates a few strong and well-known spectral clues. So Watson and his colleagues expanded their analysis to consider it. In doing so, they turned up the clear "fingerprint" of strontium. It emerged in light collected by the Very Large Telescope in Chile within a few days of the neutron-star collision. Seeing strontium in the afterglow wasn’t all that unexpected, says Brian Metzger. He’s an astrophysicist at Columbia University in New York City and not involved in the new work. Strontium, he notes, “does tell us something interesting” about the elements formed during the neutron-star collision.
(Source: https://www.sciencenewsforstudents.org/)
Which best serves as the title for the passage?
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