Consider a series of molecules in which the c atom is bonded to atoms of second-period elements: c-o, c-f, c-n, c-c, and c-b. place these bonds in order of decreasing bond length.

Explanation:

As we move along to the right in the same period, the electronegativity and the effective nuclear charge values are higher.

The tendency is that the higher these values are, the shorter the bonds will be.

With that information in mind, and looking at the periodic table, the order would be:

Where the C-F bond is the shortest among them.

"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."

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.