Answer:
.b. When she returned to work after maternity leave, she learned that her office had been relocated to the second floor
Step-by-step explanation:
The above statement correctly punctuated with a comma after the brief stop in "maternity leave". Commas and punctuations in general offer meaning to statements, and aid easier comprehension. The comma in the above statement for example makes it easier to understand the sequence in events such as that she first returned to the office before the subsequent event took place.