Tornadoes occur throughout the world, but for reasons that scientists are not fully able to discern, the great majority occur in the United States. Approximately 700 tornadoes a year occur within the United States, and this comprises three-quarters of the worldwide total. Most of the Line U.S. tornadoes take place in the Midwest and in the southern states that border the Gulf of Mexico.

In general, a tornado cuts a path of a few hundred yards and lasts less than an hour; an average tornado might propel itself at a speed of 15 or 20 miles per hour and therefore cover a distance of 20 or so miles. Tornadoes, however, can be much worse than average. The most devastating tornado on record occurred on March 18, 1925, in the states of Missouri, Illinois, and Indiana. The path of this tornado was more than 200 miles long and a mile wide. Traveling at an average speed of 60 miles per hour, the winds at the center of the storm swirled around at considerably more than 200 miles per hour. A total of 689 people died, and countless more were injured, at the hands of this killer storm.

5.The word “discern” in line 1 is closest in meaning to which of the following?

6.The word “propel” in line 6 could best be replaced by

7.Which of the following is closest in meaning to the word “devastating” in line 7?

8.The word “swirled” in line 10 is closest in meaning to