Final answer:
The common shortcut for looping a section in Arrangement mode in many applications is Ctrl + L. However, it's essential to check the specific software documentation or educational materials for confirmation as it may vary by program.
Step-by-step explanation:
The shortcut for looping a section in Arrangement mode depends on the specific software you are using, as different digital audio workstations (DAWs) may have different shortcuts. However, based on the options provided (Ctrl + L, Alt + R, Shift + Q, Ctrl + B), it's common in many applications that Ctrl + L is the shortcut used to loop a selected section in Arrangement mode. To ensure accuracy for your particular software, it's recommended that you refer to the software's documentation or the 'Before You Move On' section in the relevant chapter of your study materials where correct answers are bolded.