The HCF of 144 and 198 is

1. 6

2. 9

3. 12

4. 18

By division method:

$\begin{array}{l} 144\overline{\smash{\big)}198\smash{\big(}}\phantom{}1 \ \phantom{x}\phantom{))}\underline{-144} \ \phantom{{x^2 } 1(()}54\overline{\smash{\big)}144\smash{\big(}}\phantom{}2 \ \phantom{{x} +1xa}\underline{-108} \ \phantom{{x^2 a} + 2x()} 36\overline{\smash{\big)}54\smash{\big(}}\phantom{}1 \ \phantom{{x} +1xa+()}\underline{-36} \ \phantom{{x^2 a} + 2x++(} 18\overline{\smash{\big)}36\smash{\big(}}\phantom{}2 \ \phantom{{x} +1xa+++(}\underline{-36} \ \phantom{{x^2 a} + 2x++++(} 0 \ \end{array}$

So, HCF of 144 and 198 = 18.

Hence, option 4 is the correct option.