Final answer:
In "Daisy Miller," the phrase "a glass in one eye" refers to a monocle, which is a single lens eyeglass.
Step-by-step explanation:
The phrase "a glass in one eye" from the novella "Daisy Miller" by Henry James refers to a monocle. A monocle is a single lens eyeglass kept in position by the muscles around the eye mostly used for corrective or magnifying purposes, and it was a common accessory among certain classes in the past. It is not to be confused with sunglasses, a teardrop, or a telescope, the latter of which is an instrument composed of lenses for observing distant objects, such as the ones described by Galileo with a convex objective and a concave eyepiece that produce an upright image. In summary, the correct answer to the question is (a) Monocle.