Which of the following is the characteristic of hydrogen

单项选择题It can be inferred from the passage that the Sun’s light travels ______.

单项选择题Which sentence proves that setting the giant reflector is a delicate operation

单项选择题What does the passage mainly discuss

单项选择题According to the passage, in the late 1960s some residents of Boston were concerned with which aspect of skyscrapers

单项选择题Where in the passage does the author compare the energy consumption of skyscrapers with that of a city