Define the "work principle" for real machines:

The work accomplished by a machine will always be less than the work needed to operate the machine.
The work accomplished by a machine will always be greater than the work input required to operate the machine.
The work required to operate a machine is equal to the work which it will perform (output).

"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."

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

i belive it is water