2 sentences

1. 今天我收到一封匿名信。

   jīn​tiān wǒ shōu dào yī fēng nì​míng​xìn.

   Today I received an anonymous letter.

   Source: AI Challenger 2017

2. 昨天他收到了一封匿名信。

   zuó​tiān tā shōu dào le yī fēng nì​míng​xìn.

   He received an anonymous letter yesterday.

   Source: AI Challenger 2017