Which of the following statements is true?
a. the entropy of a system always decreases for a spontaneous process.
b. a spontaneous reaction is always a fast reaction.
c. perpetual motion machines are a possibility in the near future.
d. there is a "heat tax" for every energy transaction.
e. none of the above is true.

The correct answer is D.

Explanation:

In every process that includes an energy transaction or transition, inevitably a little amount of energy in heat form will be lost. Regardless if the process is spontaneous or not, the loss of energy (heat tax) will be present always. Also, it is impossible to make a perpetual machine, not always a spontaneous reaction will be fast, and only in certain cases the entropy could decrease during a spontaneous process.

Therefore the correct answer is D.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."