Final answer:
The sentence 'Neither the boy nor the girl was there in a class' is correct. The verb 'was' is used because both subjects, 'the boy' and 'the girl', are singular.
Step-by-step explanation:
The correct sentence is: Neither the boy nor the girl was there in a class. The choice between 'was' and 'were' depends on the subject of the sentence, in this case, 'the boy' and 'the girl' are considered singular, thus we use 'was'.
Our rule here is that when 'neither...nor' or 'either...or' connects two singular subjects, the verb should be singular. However, if one of the subjects connected by 'nor' or 'or' is plural, then the verb must be plural as well.
Learn more about Subject-Verb Agreement