Answer:
Sentence B
Step-by-step explanation:
Dependent clauses do NOT express a complete thought. They cannot stand on their own. When solving questions like this, it helps to break apart a sentence into clauses.
A. (She became angry) but* (she would not leave without her brother.)
This sentence does not contain a dependent clause because both clauses make sense; both clauses can stand on their own.
*This sentence contains a coordinating conjunction, For And Nor But Or YEt So, or FANBOYS.
B. (The diving board broke)(when she entered the pool)
This sentence contains a dependent clause. The second clause is dependent because it cannot stand on its own. It would not sound like proper English by itself.
-Happy to help, Al