Final answer:
If Marcellus is twice as tall as Dan, whose eyes are 5 cm apart, the distance between Marcellus's eyes will be 10 cm.
Step-by-step explanation:
The question asks us to determine the distance between Marcellus's eyes if he is made to be twice as tall as Dan, whose eyes are 5 cm apart. Since the sizes of features on a human scale proportionally with height, and Marcellus is twice as tall as Dan, the distance between Marcellus's eyes should be twice the distance of Dan's eyes.
Therefore, the distance between Marcellus's eyes will be 10 cm (2 times 5 cm).