Question

Is this sentence a complex sentence:
In 1999 the European Union created a new currency so that it was called the euro.

Answer 1

The sentence doesn't make much sense.

A better complex sentence:

In 1999 the European Union created a new currency that was called the euro.

Answer 2

"In 1999 the European Union created a new currency". This sentence can stand alone. "so that..." is a subordinate clause (dependent clause), and if read by just that portion it wouldn't make much sense. When trying to figure out if a sentence is complex simply split it into two sentences and read it out loud. It also is helpful to look at a list of subordinate conjunctions

Answer 3

Ms. Sue is right. As it stands, the sentence makes no sense. It is, however, a complex sentence in a grammatical sense. Rune is right, too, but his explanation would confound me. Study this for a clear understanding of simple, compound, and complex sentences:

http://www2.ivcc.edu/rambo/eng1001/sentences.htm