Two of the most dangerous storms which hit America are hurricanes and tornadoes. They are very much feared by anyone who may live in the path of their destruction and cause millions of dollars of damage to life and property every year. If one should travel inland across the Great Plains and the Prairie   states of America, one will mostly not experience a hurricane, but there is another kind of storm in the Midwest which is equally feared. It is called a tornado. Tornados are violent low-pressured storms with an intense updraft   near their center which is capable of lifting quite heavy objects from the ground. A tornado,therefore, is a dark, funnel-shaped cloud containing violently rotating air. It can pick up trees and cars right into the air and even uplift heavier objects such as homes and railway cars. Like a vacuum cleaner across a rug, it sucks up into anything which may lie in its path. These storms occur most often during the summer months and are noticeable by their strong wind and lack of rain. The sky turns black as dust is sucked up into the air. Tornadoes travel normally around 60 kilometers per hour and the winds can reach 800 kilometers per hour in the most violent storms. Tornados are most frequent in the United States east of the Rocky Mountains and especially in the central plains area of the Mississippi basin where about 150 occur each year. Tornados may also strike the southern states in winter and have even seen known to develop in the northeast. Both hurricanes and tornados cause millions of dollars worth of damage each year. Today they can be predicted more easily than in the past, but they cannot be stopped or ignored. When they come, they must be endured with the hope that one survives their fury and wraths. A tornado can be compared to  _  .
a washing machine a jet plane a fire fighting truck a vacuum cleaner