Teacher: Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Who did the Han Chinese want to help the Khitan no I mean the Mongols fight?
Solution: Who did the Han Chinese want to help the Mongols fight?
Reason: The input initially means Khitan and then changes to Mongols, hence this is correct.

Now, solve this instance: During what time frame limited to students no were the core classes limited to only 15 students?
Student:
During what time frame were the core classes limited to only 15 students?