(A) Mixture of water and milk -> Milk is a colloid with fat globules and proteins dispersed in water, shows Tyndall Effect.
(B) Sunlight passing through a canopy of dense forest -> Dust particles, water droplets, and aerosols in air scatter light, shows Tyndall Effect.
(C) Solution of copper sulphate -> This is a true solution with molecularly dispersed particles too small to scatter light, does NOT show Tyndall Effect.
(D) Light entering a smoke-filled room through a small hole -> Smoke is a colloidal aerosol with tiny solid particles in air, shows Tyndall Effect.
Hence, Option 2: (A), (B) and (D) only -> The Tyndall Effect occurs only in colloids and suspensions where particles are large enough (1-1000 nm) to scatter light. Copper sulphate forms a true solution, not a colloid, so it cannot show this effect. -> correct