Mostly, waves ... by wind blowing over the surface of the sea.
A) are formed ( my answer )
B) formed ( correct according to my book )
Should I burn my book ?
Mostly, waves ... by wind blowing over the surface of the sea.
A) are formed ( my answer )
B) formed ( correct according to my book )
Should I burn my book ?
They are both correct, but "are formed" is much better, for several reasons:
Even the following is better than simply "formed":
Mostly, waves were formed by wind blowing over the surface of the sea.
Bottom line: your choice was the better choice.
Should I burn my book?
Definitely not. That is a useless process, and it only creates pollution. You can save the book and use the pages one by one, on an as-needed basis, to start camp fires - please attend those fires responsibly, you do not want to burn the entire planet.