The chance of a student passing an exam is $20 \%$. The chance of a student passing the exam and getting above $90 \%$ marks in it is $5 \%$. GIVEN that a student passes the examination, the probability that the student gets above $90 \%$ marks is

- $\dfrac{1}{18} \\ $
- $\dfrac{1}{4} \\$
- $\dfrac{2}{9} \\$
- $\dfrac{5}{18}$