The correct answer is A. F10.
To use Dr/Cr instead of To/By during Voucher entry or vice versa, press F10. This will toggle between the two modes.
F10 is a function key that is often used to access menus or perform special actions. In the case of Sage 50, pressing F10 will toggle between the Dr/Cr and To/By modes during voucher entry.
Dr/Cr stands for Debit and Credit. Debit is the left side of a T-account, and Credit is the right side. To/By stands for To and By. To is the account that is being debited, and By is the account that is being credited.
When you are entering a voucher, you will need to specify which accounts are being debited and credited. You can do this by selecting the appropriate accounts from the drop-down lists.
If you want to use Dr/Cr instead of To/By, you can press F10. This will toggle between the two modes. In Dr/Cr mode, you will need to specify the debit and credit amounts. In To/By mode, you will need to specify the To and By accounts.
I hope this helps!