Question 4. The main idea of paragraphs 3 and 4 is that _______. -----Passage 1----- (Para. 1) At one time a traveler could learn about a region by looking at the houses, for example, he or she could understand what building materials were available. In areas with many wood houses, the traveler would have guessed that there were nearby forests. Stone houses would have indicated that stones were easy to get. However, a closer look at the houses would have told the traveler even more about the area. (Para. 2) People used to build houses that fitted the climate of their areas. For example, in desert regions there is a big difference between daytime and nighttime temperatures. Therefore, many desert people built houses with very thick walls. These thick walls served a useful purpose in the houses. For example, in the winter the thick walls absorbed the sun’s warmth during the day and radiated the heat at night. Desert people were relatively comfortable in their homes, or residences, at all times because they built them to fit the desert climate. (Para. 3) Then the supply of fuel for electricity became both cheap and easy to get. The effect on housing was immediate. People began to build their homes according to fashion instead of utility. Houses no longer reflected the availability of building materials or climate. (Para. 4) Houses with steep roofs could be found in the tropics, the warm regions of the Earth, even though these pointed roofs originated in snowy regions of the world. Heavy snow falls off a slanted roof. Another example is the use of glass. Houses made almost completely of glass could be found in very cold places. Yet ordinary glass does not insulate well because it neither keeps out cold air nor keeps in warm air. As long as fuel was cheap and easy to get, people could build any type of house any place. -----Question 4. The main idea of paragraphs 3 and 4 is that _______.