她口角边渐渐的有了笑影，脸上也白胖了。（）

她口角边渐渐的有了笑影，脸上也白胖了。（）
A、Little by little the trace of a smile appeared at the corners of her mouth， but her face became whiter and plumper.
B、Little by little the trace of a smile appeared at the corners of her mouth， so her face became whiter and plumper.
C、Little by little the trace of a smile appeared at the corners of her mouth， while her face became whiter and plumper.
D、Little by little the trace of a smile appeared at the corners of her mouth， when her face became whiter and plumper.
正确答案：C