Task: Text Completion
Input (English): [header] How to buy lenses for your digital slr [title] Pick a focal length designed for the type of pictures you take. [step] The focal length is represented by two numbers with a dash in between (i.e. , 18-55). It marks the distance from the camera lens to the sensor. <sep> (A) Common focal length may be 21 , 60, and 40. In contrast , 100 mm is the most popular focal length. (B) A wider range makes a camera better at taking photos from a distance. A shorter range means a camera will be better at shooting single scenes up close. (C) You can purchase frames that have this length or shorter depending on the lens's curve. [substeps] The focal length will be displayed at the bottom of the camera. (D) [substeps] In this case, you will give the focal length at 30 millimetres (about the number of millimetres or inches). To save time you can use 1/10 or 60 millimetres instead of 1/13 and 3/5 millimetres.
Output (English): B