By definition, a complex sentence contains two or more clauses. A clause is a grammatical unit: whenever a sentence contains a subject and a predicate, it is a clause. Examples of simple sentences are A. and D. In the case of B. and C., each of them contain two clauses. Sentence B.: clause 1 = "When you father( subject) comes home (predicate)"; clause 2 = "he (subject) will be upset (predicate)".
