4 sentences

1. 中国已经步入了老龄化社会。

   Zhōng​guó yǐ​jīng bù​rù le lǎo​líng​huà shè​huì.

   China has entered an aging society.

   Source: Dong Chinese Dictionary

2. 由于人口老龄化，该国的劳动力正在减少。

   yóu​yú rén​kǒu lǎo​líng​huà, gāi guó de láo​dòng​lì zhèng​zài jiǎn​shǎo.

   Due to the aging population, the country's labor force is shrinking.

   Source: Dong Chinese Dictionary

3. 如何应对人口老龄化是当今社会的重大课题。

   rú​hé yìng​duì rén​kǒu lǎo​líng​huà shì dāng​jīn shè​huì de zhòng​dà kè​tí.

   How to deal with an aging population is a major issue in today's society.

   Source: Dong Chinese Dictionary

4. 由于人口老龄化，这个国家的征兵工作变得越来越困难。

   yóu​yú rén​kǒu lǎo​líng​huà, zhè​ge guó​jiā de zhēng​bīng gōng​zuò biàn de yuè​lái​yuè kùn​nan.

   Conscription has become increasingly difficult in this country due to its aging population.

   Source: Dong Chinese Dictionary