Concept:The subject phrase "Every one of the boys" is singular, so it must take a singular verb.
Explanation:The head word in the subject is "every one", not "boys".
The words "of the boys" only form a prepositional phrase that describes the head word.
Because "every one" refers to each individual boy separately, it acts as a single subject.
A singular subject must agree with a singular verb in the present tense.
Therefore, the correct verb form is "seems".
In addition, "seem" is a stative verb, so continuous forms such as "is seeming" and "was seeming" are not appropriate here.
The word "seem" is the plural present tense form and does not match the singular subject "every one".
Thus, the sentence correctly reads: "Every one of the boys seems excited about the picnic."
Answer:D. seems