B. density is the right answer
The molecule is non-polar, because the difference in electronegativity between the two sides of the structure equals 0. The electronegativity difference between O (3.5) and C(2.5) is 1 and also on the other side, cancelling each other.
The correct answer is option B. i.e. the number of protons is increased.
In beta-particle emission, a neutron is changed into proton, electron and electron neutrino. The electron is emitted as beta particle and the proton remains inside the atom. Thus, the mass number remains same but the atomic number increases by one.
