4 sentences

1. 我郑重宣誓，我一定会这么做。

   wǒ zhèng​zhòng xuān​shì, wǒ yī​dìng huì zhè​me zuò.

   I solemnly swear to do so.

   Source: OpenSubtitles

2. 他郑重声明自己与这件事无关。

   tā zhèng​zhòng shēng​míng zì​jǐ yǔ zhè jiàn shì wú​guān.

   He solemnly declared that he had nothing to do with this matter.

   Source: Dong Chinese Dictionary

3. 他郑重地向大家宣布了这个消息。

   tā zhèng​zhòng de xiàng dà​jiā xuān​bù le zhè​gè xiāo​xi.

   He solemnly announced the news to everyone.

   Source: Dong Chinese Dictionary

4. 面对大家的关切，他郑重地作出了承诺。

   miàn​duì dà​jiā de guān​qiè, tā zhèng​zhòng de zuò​chū le chéng​nuò.

   In the face of everyone's concern, he solemnly made a promise.

   Source: Dong Chinese Dictionary