Here is the original item:
His arms full of expensive science fiction paperbacks, (A) Cary remembered (B) that next semester's tuition was due in two weeks. (C) Making a trip to the library instead of the bookstore a better financial decision.
You wanted to do this:
His arms full of expensive science fiction paperbacks Cary remembered that next semester's tuition was due in two weeks. Making a trip to the library instead of the bookstore a better financial decision.

Removing the comma after paperbacks is incorrect. You must connect an introductory phrase with a comma.

You might want to review the rules.

Go back to the item to try again.