There are several ways in which Americans  1        customs are different from those in other parts of the worm．A guest invited to dinner is  2         to arrive on time. The use of the knife and fork is often different．The fork is used mostly in the right hand．It 3 __________the food without help from the knife，which is 4______used only to cut meat or potatoes, and is placed to the right of the plate when in use．And while in many places the napkin(餐巾)is put around the neck，here it is put on the lap．Finally，when Americans eat certain foods，they use their  5_______. For example，at picnics they eat chicken，pizzas，and so on with their hands only

Pessimistic forecasts say that there is only enough coal for 450 years，enough natural gas for 50 years and that oil might run out in 30 years．

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