1. be obliged to 有責任/義務做某事
It seems he has no ability to raise himself, but he never thinks he is obliged to do so.
他似乎沒有能力養活自己的能力，但他也從來不認為自己有責任這么做um;.nTgT9YnfG*c-p。

2. play a pivotal role in 發揮關鍵作用
Despite its resurgence, few believe the party will play a pivotal role in national politics.
盡管日共正在復蘇，然而極少有人相信該黨會在國內政治中起到中堅作用8&&7lzW,!yQB。

3. pose a challenge for sb.構成挑戰
A 10 is a book that might even pose a challenge for us, and a 4 is probably around the easiest book we would recommend.
一本難度為10的書即使對我們而言也是一個挑戰，而一本難度為4的大概是我們推薦的書中最容易的T6bR&#[LHC-。

4. rely disproportionately on 嚴重依賴于
People with HIV/AIDS rely disproportionately on the public sector for their health care, particularly Medicaid.
艾滋病患者的醫療保健嚴重依賴公共部門，尤其是醫療補助計劃6CKe]~EHM.b#Y6。