The Titanic _______ the Atlantic when it _______ an iceberg.
was crossing / struck
had crossed / was striking
crossed / had struck
is crossing / strikes
Correct answer: A
The structure S + was/ were + V-ing when S + Ved is used to talk about an action that happened to interfere with an ongoing event in the past.
Translated: The Titanic was sailing through the Atlantic Ocean when it hit a driftwood.