Among the given options, only sentence (A) is grammatically correct. The others have grammatical errors:
- (B) "Except he all were present" is incorrect; it should be "Except him, all were present."
- (C) "I, who is your teacher, will teach you" is incorrect; it should be "I, who am your teacher, will teach you."
- (D) "Waters are necessary for human beings" is incorrect; it should be "Water is necessary for human beings."