他每天都会查看信箱，期待收到朋友的来信。

He checks the mailbox every day, hoping to receive ___letters from his friends.

她正在学习如何书写这些字母。

She is learning how to write these ___letters.

她获得了文学学位后成为了一名作家。

She became a writer after receiving her ___degree in literature.