單格填空第 1 題
In parts of the Arctic, the land grades into the landfast ice so ______ that you can walk off the coast and not know you are over the hidden sea.
| Blank |
|---|
| (A) permanently |
| (B) imperceptibly |
| (C) irregularly |
| (D) precariously |
| (E) relentlessly |
出處：OG, p.50, #3 and PP2, Test Preview, #6