I would write them all out but im lazy. change the noun after the word by and make that the subject of the sentence followed by the verb and the rest of the sentence :)
The answer is A. Use the gerund at the beginning to show action,
complete the sentence with subject and verb that show why the action was
completed. This concise method is widely used and generally understood
by readers at first glance. Other arrangements may technically work but
will likely cause confusion.
