Give the decreasing order of covalent character of the following compounds.
a. I. `GeCl_(2)` II. `GeCl_(4)` III. `SnCl_(2)` IV. `SnCl_(4)`
V. `PbCl_(2)` VI. `PbCl_(4)`
b. I. `CH_(4)` II. `NH_(3)` III. `H_(2)O` IV. HF
c. I. HF II. HCl III. HBr IV. HI
d. I. AgI II. NaI III. CuI IV. NaCl
A. I and IV
B. II and III
C. I and II
D. III and IV