1.I can't help but be angry with him.
2. He couldn't do the job. - No wonder he never knew how to do anything.
3. I was very strong as a child, I could even swim across the river.
4. If you don't call tomorrow, there's nothing I can do for you.
5. I thought I wouldn't be able to open the door since the lock had rusted (to get rusty) but eventually I was able to turn the key and the door opened.
6. I could not understand anything, although I listened very attentively