The world economy in the ninth cen tury had two powerful engin es. One was Tang dyn asty Chi na, an empire 1 (stretch)from the South China Sea to the bordersof Persia, with ports ope n to
表示“强调某种状态在特定明显或不明显”的句型This is especially true if/when we consider the fact that/when it comes to/in terms of 当我们考虑··的时候，这一点尤为正确It is not even always true that··· ···并不是总是正确的
