她试图保持坚强，但内心充满了悲伤。

She tried to stay strong, but ___inside, she was filled with grief.

尽管他很生气，但内心仍保持着深深的平静。

Despite his anger, a deep calmness remained ___inside.

他微笑着，但内心感到非常孤独。

He smiled, but ___inside, he felt very lonely.