grin

他脸上露出淘气的笑容。

He had a mischievous ___grin on his face.

她的笑容很有感染力，让每个人都笑了。

Her ___grin was infectious, making everyone smile.

当他获奖时，他忍不住咧开嘴笑了。

He couldn't help but ___grin from ear to ear when he won the prize.