a smile appeared on his face这里appear为什么要用过去式?

a smile appeared on his face这里appear为什么要用过去式? A big smile appeared on his face. A smile appeared on her face是主系表吗 A smile ( ) on his face. there is a relaxed smile on his face.为什么用relaxed?不用relaxing? There is -a---- a charming smile on his face Benny said,with a big smile on his face是什么意思? there was a pleasant smile on his face There was a pleasant smile on his face. After he worked out the solution,appeared a smile on his fac He said with a smile on his face 还是in his face __a big smile on his face