extent
1.extent前面的介词是to，如下面各个习语：
- to any extent, to some extent, to what extent, to a great extent, to a surprising extent, to the utmost extent, to a certain extent, to the same extent, to such an extent that..., to the extent of（或that...）
2.下面两句意思相同：
- He grew more and more absorbed in his work, to such an extent that he almost forgot his meals.
- He grew more and more absorbed in his work, to the extent that he almost forgot his meals.
