I received this correction today:

“You haven’t heard from us in awhile. 🙂 You might have updated this since our last download, but Natalie and Spencer just finished taking test LIV. #28 is marked on the answer key as being C. to come. Natalie thinks it should be B to run. Is that right? Just wanted to double check.”

She is right.

In test 54, question 28 is:

Mater imperat fratri mei ut currat.    

A) to walk     B) to run     C) to come 

The answer is B).  The key may say that the answer is C).

Again, if you spot any mistakes, please let me know!