The correct order of increasing covalent character is

 $\mathrm{KCl}$ and ${\mathrm{CaCl}}_2$ has ionic character

Silicon tetrachloride has maximum covalent character, as silicon cation has maximum charge.
Potassium chloride has minimum covalent character, as potassium cation has minimum charge because,

The covalent character of ionic compound can be determined by Fajan's rule, which states that cation with higher positive charge has greater covalent character than cation with lower positive charge.

Hence, the correct option is  (B) $\mathrm{KCl}<{\mathrm{CaCl}}_2<{\mathrm{AlCl}}_3<{\mathrm{SiCl}}_4$.