Imagine a classmate of yours, Sarah, is having trouble seein…

Imagine a classmate of yours, Sarah, is having trouble seeing their specimen on the microscope at higher magnifications. Sarah is able to see the specimen at 4x moderately, but barely at 10x, and not at all while using the 40x objective lens. Sarah keeps saying the image is very dim while using the higher magnification objective lenses. Which of the following pieces of advice would be BEST to help your classmate find the specimen in her microscope?