1. could
I wish I could.
The policeman talked to the children in as friendly a manner as he could.
The dying man made an effort to say something, but could not.
The war on Iraq is a volatile subject of political debate; any wrong word and a heated argument could spark.
An international trade ban could be the last straw for that country's economy.
I'm so embarrassed I could dig a hole and crawl into it.
Tom pressed his ear against the wall to see if he could hear what his parents were discussing in the next room.
Tom can already play the drums better than I could at his age.
What kind of woman could love a guy like Tom?
According to some scholars, a major earthquake could occur at any moment now.
Would I only work on weekends if I could? Of course, I would.
He believed that blacks could win their fight for equal rights without violence.
The grenade blew up before the terrorist could throw it, and his arm was blown off!
A good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation.
I could stand here with you forever, just gazing off into the sea.