Which is a complex sentence?

 - Kenny picked raspberries in the field until his fingertips were stained red.
 - In June, Sue and Mitchell will graduate with honors from Clarksville High School.
The first sentence is the complex sentence. It is made up of an independent clause and a dependent clause. The dependent clause begins with the subordinating conjunction until.
Kenny picked raspberries in the field until his fingertips were stained red.