In English, complex sentences have two or more clauses. A clause has a subject and verb. In the sentence "She was late, because the bus had stopped everywhere", the subjects are "she" and "bus" and the verbs are "was" and "stopped".Take care to learn the difference between simple, compound and complex sentences. A simple sentence has a single clause: "She was late". A compound sentence has two clauses joined by a simple connective such as "and", "but" or "or". Here is an example of a compound sentence: "She was late and the bus stopped everywhere". A complex sentence has two clauses and also explains the relationship between the two: "She was late BECAUSE the bus had stopped everywhere". The type of word needed to explain this relationship is a connective.
You can test your understanding of connectives in the quizzes devoted to the topic. Here you can test your ability to distinguish between simple, compound and complex sentences. Remember that a phrase is not the same as a clause, but is instead a cluster of words used for a single function. In the previous sentence "a cluster of words" is a noun phrase (you can see there is no verb in that group of words, so it cannot be a clause).
If you enjoy this quiz, there are more quizzes about sentences to play!