(A) : As number of bonds between two atoms increases, bond length increases.
(R): Bond length order between two carbon atoms is $\mathrm{C}-\mathrm{C}>\mathrm{C}=\mathrm{C}>\mathrm{C}\equiv \mathrm{C}$

Order of bond energy= $\mathrm{C}\equiv \mathrm{C}>\mathrm{C}=\mathrm{C}>\mathrm{C}-\mathrm{C}$

$\mathrm{Bond} \mathrm{energy} \mathrm{\alpha } \mathrm{Bond} \mathrm{order} \mathrm{\alpha } \frac{1}{\mathrm{Bond} \mathrm{length}}$

Bond energy of the compound is directly proportional to the bond order.

Similarly, Bond length of the compound is inversely proportional to the bond order.
Hence when bond order increases, bond length decreases and bond energy increases.