Seeing how happy she looked, I was certain that Jack had proposed to her. A. I knew just by looking at her that she was in love with Jack. B. The happy look on her face convinced me that sh

I knew just by looking at her that she was in love with Jack.

The happy look on her face convinced me that she'd received a marriage proposal from Jack.

Judging by the happy look on her face, I guess that she accepted Jack's marriage proposal.

When I talked to her, I learnt that she was so happy because Jack had proposed to her.