When performing a fundoscopic examination with an ophthalmoscope, why might a clinician need to adjust the lens?

a. To compensate for near-sightedness or far-sightedness of both the patient and the examiner, ensuring a clear view of the retina.
b. To change the color of the light for better visualization of different retinal layers.
c. To modify the size of the light beam based on the patient's pupil size.
d. To alter the intensity of the light to accommodate varying levels of room brightness.
e. To switch between magnified and non-magnified views of the retina.