Why should you always begin focusing on a specimen with the 4x objective lens in place?

You should always begin focusing on a specimen with the 4x objective lens because it provides the widest field of view, allowing you to locate the specimen easily. This lower magnification also offers a greater depth of field, making it easier to find and center the specimen before switching to higher magnifications. Additionally, starting with the 4x lens minimizes the risk of crashing the objective lens into the slide, which can damage both the slide and the lens.