The best way to complete the sentence and form a compound sentence is "I called her many times, but she didn't answer the phone."
What is a compound sentence?
A compound sentence is formed when we join two independent clauses by connecting them with a coordinating conjunction - for, and, nor, but, or, yet, so.
For the sentence we are supposed to complete, the best conjunction is "but", which indicates a contrast between the two ideas. I called. Normally, she would answer. But, she did not answer this time.
Learn more about compound sentences here:
https://brainly.com/question/13779006
