BBC在线收听下载:伦敦科学家发现让牙齿自行修复的方法

短语讲解：

1. The Pentagon said a unit of commandos,tasked with tracking down jihadist leaders, carried out the operation on Sunday near the city of Dayr az Zawr.

carry out 进行; 执行; 完成
例句：The Social Democrats could still carry out their threat to leave the government
社会民主党人仍有可能将其退出政府的威胁付诸实施。

2. A BBC investigation has identified the man accused of organizing two attacks on tourist targets in Tunisia in 2015.

accuse of 指责，控告
例句：They may even accuse the child of disloyalty.
他们甚至责备孩子不忠诚。

3. Three West African Presidents will visit The Gambia on Wednesday to press Yayha Jammeh to step down.

step down 退休，辞职
例句：If I were to be, I would step down and raise my voice immediately.
一旦我弄清楚了，我会立即辞职站出来表态。