to be hard

• 难以回答

  be difficult to answer

• 难以启齿

  be hard to say

• 难以置信

  be hard to believe

• 难以想象

  be hard to imagine

• 难以实现

  be difficult to achieve

• 难以克服

  be hard to overcome

• 难以胜任

  be unequal to the task

• 难以磨灭的印象

  indelible impression

• 难以名状

  be indescribable