5 sentences

1. 它们没有光滑的表面。

   tā​men méi​yǒu guāng​huá de biǎo​miàn.

   They don't have a smooth surface.

   Source: AI Challenger 2017

2. 地球比台球更光滑。

   dì​qiú bǐ tái​qiú gèng guāng​huá.

   The Earth is smoother than a billiard ball.

   Source: Tatoeba

3. 只剩下他的脸完全光滑。

   zhǐ shèng xià tā de liǎn wán​quán guāng​huá.

   Only his face remained completely smooth.

   Source: CCMatrix

4. 盒子的表面很光滑。

   hé​zi de biǎo​miàn hěn guāng​huá.

   The surface of the box is very smooth.

   Source: CCMatrix

5. 提醒：除了沙子，光滑的鹅卵石也是好选择。

   tí​xǐng: chú​le shā​zi, guāng​huá de é​luǎn​shí yě​shì hǎo xuǎn​zé.

   Reminder: In addition to sand, smooth pebbles are also a good choice.

   Source: CCMatrix