The teacher promised
that he will explain it
if they come
before school the following day E. No error
Answer is Right!
Answer is Wrong!
The correct answer is: E. No error
The sentence is grammatically correct. The teacher promised that he will explain it if they come before school the following day. The teacher is the subject of the sentence, and promised is the verb. That he will explain it is a subordinate clause that provides additional information about the promise. If they come is a conditional clause that states the condition under which the teacher will explain it. Before school the following day is a prepositional phrase that tells when the teacher will explain it.
The sentence is clear and easy to understand. The meaning of the sentence is not affected by any of the options.