The underlined word "upbeat" in paragraph 2 probably means ______.

单项选择题The author discusses computing machines in the first paragraph primarily in order to ______.

单项选择题The author implies that scientists develop a healthy skepticism because they are aware that ______.

单项选择题According to the passage, scientists are skeptical toward their equations because scientists ______.

单项选择题What can we infer from the passage

单项选择题Assumptions are important for critical readers because they can help readers to ______.