Match Column I with Column II

i-b; ii-c; iii-d;iv-a

The correct answer is option 1. i-b; ii-c; iii-d;iv-a.

Here is the breakdown of the dispersed phase (what's being dispersed) and the dispersion medium (what the dispersed phase is in) for each type of colloid:

i. Solid in liquid: b. Sol: This is the correct match. Sols are suspensions where solid particles are dispersed in a liquid medium. Examples include ferric hydroxide sol (solid \(Fe(OH)_3\) particles in water).

ii. Liquid in solid: c. Gel: This is also correct. Gels are dispersions where a liquid is trapped within a solid network. Examples include gelatin gels (water trapped in a protein network).

iii. Liquid in liquid: d. Emulsion: This is another correct match. Emulsions are dispersions where one liquid is dispersed as droplets in another immiscible liquid. Examples include milk (fat droplets in water) and oil and vinegar salad dressing (oil droplets in vinegar).

iv. Gas in liquid: a. Foam: This is the correct pairing. Foams are dispersions where a gas is dispersed in a liquid medium. Examples include whipped cream (air bubbles in cream) and soap suds (air bubbles in soapy water).