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

单项选择题The main purpose of the passage is to ______.

单项选择题According to the passage, what is one disadvantage of skyscrapers that have mirrored walls