Https://www.enotes.com/topics/zookeepers-wife
there is a summary of the book, if you dont know the answer i suggest you read the book or read the summary (:
Answer:
If you believe in and trust yourself, no one else can ever shake your confidence.
I want to go to the concert, but I'm not sure if I will be able to make it.
This one uses correct comma usage to join two independent clauses, the comma goes before the coordinating conjunction (but).
The semicolon would only be used before the coordinating conjunction if in the first clause a comma was used. But that's not the case so the answer with the semicolon is thus incorrect.