篝火熄灭后，木炭还在闷烧，冒出缕缕青烟。

After the campfire died out, the charcoal continued to ___smoulder, sending up wisps of smoke.

尽管他表面平静，愤怒的情绪仍在内心暗燃。

Though he appeared calm, anger ___smouldered within him.