Step 1: Rule of subject-verb agreement.
"Everybody" is singular, so it takes a singular verb.
Step 2: Apply the rule.
Correct verb: "wants."
Step 3: Eliminate others.
(A) want – plural verb, incorrect.
(B) will want – future tense, not required.
(C) wanting – not grammatically correct here.
Identify the part of the sentence that contains a grammatical error:
Each of the boys have submitted their assignment on time.