tā liǎ / zài / kè jiān / bāi / shǒu / wàn / wéi guān / de / tóng xué / dōu / zài / hǎn / jiā yóu

他俩在课间掰手腕，围观的同学都在喊加油。

The two of them arm-wrestled during the break, and the classmates watching were all cheering.