3 sentences

1. 考试没考好，他的情绪非常低落。

   kǎo​shì méi kǎo hǎo, tā de qíng​xù fēi​cháng dī​luò.

   He was in very low spirits because he didn't do well on the exam.

   Source: Dong Chinese Dictionary

2. 他这个人很情绪化，一点小事就会让他心情低落。

   tā zhè gè rén hěn qíng​xù​huà, yī​diǎn xiǎo​shì jiù huì ràng tā xīn​qíng dī​luò.

   He is very temperamental; even the slightest thing can make him feel down.

   Source: Dong Chinese Dictionary

3. 长期以来，该工厂的生产水平一直低落。

   cháng​qī yǐ​lái, gāi gōng​chǎng de shēng​chǎn shuǐ​píng yī​zhí dī​luò.

   The production level of this factory has been low for a long time.

   Source: Dong Chinese Dictionary