Question

 85. 父親聽到這個消息很興奮。(excited)

86. 不經歷風雨，怎能見彩虹。(without)

87. 眾所周知，他的成功完全是努力的結果。(due to)

88. 當你懷疑自己的時候，不要忘了最重要的是建立自信。(doubt)

89. 為了按時完成任務，志愿者們正竭盡全力把復雜的問題簡單化。(simplify)

Answer 1

85. Father was very excited to hear the news/when he heard the news.

at the news/(on) hearing the news 

86. There is no rainbow without wind and rain.

   How can you see the rainbow without going through the storm?

87. It is known to all that his success is entirely/totally/completely due to his hard work.

       /As is known to all, his success is entirely/totally/completely due to his hard work.

       /We all know that his success is entirely/totally/completely due to his hard work.

88. When you doubt yourself, don’t forget that it is the most important (thing) to build up self-confidence.

89. In order to accomplish/finish/complete the task in time, the volunteers are trying their best/doing all that/what they can to simplify the difficult/complicated matters.