Which of the following is not permissible?

Which of the following is not a permissible resonating form?

Which of the following has least permissible limit in drinking water ?

Which one of the following is the permissible level of noise in a silent zone at daytime?

Which of the electron is not permissible arrangement of electrons in an atom?

Consider the following sets of quantum numbers: Which of the below setting is not permissible arrangement of electrons in an atom?

Which of the followiong has least permissible limit in drinking water