Concept:The subject "Every one" is singular, so it needs a singular verb.
Explanation:The phrase "of the students" is a prepositional phrase and does not decide the verb number.
The true subject is "Every one", which is singular.
Therefore, the correct verb form is the singular present tense "seems".
The options "was seeming" and "is seeming" are continuous forms, which are not suitable here.
"Seem" is plural and does not agree with a singular subject.
Answer:The correct option is D: "seems".
Complete sentence: Every one of the students seems to be excited about the excursion.