练习材料：L20-1：Pioneerpilots In 1908 Lord Northcliffe offered a prize of $1,...

练习材料：L19-2：A very dear cat Mrs. Ramsay was instructed to place the money...

L19-1：A very dear cat Kidnappers are rarely interested in animals, but t...

练习材料： L18-2：Electric currents in modern art Oddly shaped forms that are ...

练习材料： L18-1：Electric currents in modern art Modern sculpture rarely surp...

L17-2：The longest suspension bridge in the world Two great towers suppor...

L17-1：The longest suspension bridge in the world Verrazano, an Italian a...

L16-2：Mary had a little lamb After telling several of his friends about ...

L16-1：Mary had a little lamb MaryandherhusbandDimitrilivedinthetinyvilla...