scratch gravel

例句：

1. 1. Thedog was scratching at the door with its claws.
   那只狗用爪子在门上挠。
2. 2. She scratched her arm and it stung.
   她挠了挠手臂，很疼。
3. 3. He scratched his head in confusion.
   他困惑地挠了挠头。