Eyepiece graticule calibrates for actual measurements but doesn't enable uncalibrated actual size comparisons Steps:

• Identify eyepiece graticule as a scale in the eyepiece for viewing specimen images under microscope objectives.
• Note it measures in arbitrary divisions, requiring calibration for real units like micrometers.
• Use stage micrometer (known scale) under same objective (e.g., ×10) to match divisions and calibrate graticule.
• Conclude: calibration with stage micrometer is direct use (✓); comparing actual cell diameters needs calibration first, so not possible without it (x).

Why B is correct:

• Eyepiece graticule definition: tool calibrated by aligning its divisions with stage micrometer's known 10 μm or 100 μm intervals under specific objective for accurate scaling.

Why the others are wrong:

• A: Wrongly allows uncalibrated cell comparison (needs actual sizes) and rejects valid calibration step.
• C: Falsely rejects both; calibration is a core use.
• D: Identical to C, so doubly rejects valid calibration.

Final answer: B