1. It was difficult for Kim to solve the problem.
Kim had (
)(
) the problem.
2. As I had seen Rex before, I could easily recognize him.
(
) Rex before, I could easily recognize him.
3. I'm playing tennis if the weather is good enough.
I'm playing tennis, (
) permitting.
4. If we judge from the look of the sky, it may rain soon.
(
) the look of the sky, it may rain soon.