The covalent radii of atoms A and B are $$r_A$$ and $$r_B$$ respectively. The covalent bond length and total length of $$AB$$ molecule are respectively  :

A

$$(r_A + r_B)$$, $$2(r_A + r_B)$$

B

$$\frac{1}{2}(r_A + r_B)$$, $$(r_A + r_B)$$

C

$$(r_A + r_B)$$, $$(r_A + r_B)$$

D

$$2(r_A + r_B)$$, $$\frac{1}{2}(r_A + r_B)$$