Which of the following mixtures show Tyndall effect?

a) $Aq.NaCl$

b) Aq. Ferric hydroxide

c) $NaCl$ in benzene

d) Aq. urea

e) Aq. Starch

Tyndall effect is the scattering of a light beam by a medium containing microscopic suspended particles, such as smoke or dust in a room, which makes a light beam entering a window visible. 

Sodium chloride, glucose, and urea in aqueous solution are real solutions. 

In a solution, the particles are incredibly tiny. They therefore do not exhibit the Tyndall effect. 

It is concluded that aqueous urea and aqueous NaCl solutions do not exhibit the Tyndall effect. 

Hence the correct option is (A).