Final answer:
The second electron affinity for halogens and all elements is always positive, not almost zero, because it involves adding an electron to an already negatively charged ion which requires energy due to increased electron-electron repulsion. The correct answer to the question is B. is always positive.
Step-by-step explanation:
The question is related to the concept of electron affinity in chemistry, specifically regarding the second electron affinities of halogens. The assertion that the second electron affinity (E.A.) for halogens is almost zero is incorrect. In fact, the second electron affinity is always positive because adding an extra electron to an already negatively charged ion is an endothermic process that requires energy. This is due to increased electron-electron repulsions which are stronger than the attraction of the nucleus for the extra electron.
While the first electron affinity can release energy and thus be negative, as is the case for chlorine (with an E.A. value of -348 kJ/mol which is the highest of any element), the second electron affinity involves adding an electron to a negative ion, which is less favorable. For example, oxygen has a first electron affinity of -141 kJ/mol but a second electron affinity of +744 kJ/mol, indicating that energy is absorbed in the process of adding the second electron.
To address the options presented in the question, the correct option that describes second electron affinity is B. is always positive.