A <u>complex sentence</u> is formed by an independant clause and a subordinate clause. In the example provided, the independant clause is "my nose runs constantly" and the subordinate clause is "when I get a cold".
The rest of the options do not apply since a <u>simple sentence</u> is formed by just an independant clause. A <u>compound sentence</u> is formed by two independant clauses joined by a semicolon or coordinating conjunction.
A <u>compound-complex sentence</u> is formed by 2 independant clauses and a subordinate one.