Review the item:
Jackie always sat in the front row because
she liked to focus on the lecture and take good notes, the excessive spitting
of her Latin professor, however, drove her to the back of the room.
The blank space between row and because is completely correct. Jackie always sat in the front row is a main clause. Because she liked to focus on the lecture and take good notes is a subordinate clause; it needs to be connected to the main clause that comes before it.
When a subordinate clause follows a main clause, you usually need no punctuation between them.
For future reference, you should remember that 99 percent of the time you will not use a comma before because. It is a common mistake that is easy to avoid.