1 sentence

1. 心脏是一个肌肉发达的器官，所以它工作的越多，它就变得越强壮。

   xīn​zàng shì yī​ge jī​ròu​fā​dá de qì​guān, suǒ​yǐ tā gōng​zuò de yuè duō, tā jiù biàn​de yuè qiáng​zhuàng.

   The heart is a muscular organ, so the more it works, the stronger it becomes.

   Source: CCMatrix