Option 2nd - a mixture of solid particles in a liquid.
<h2>Explanation:
</h2>
For a Mixture of two immiscible liquids (for example water and oil) it is not possible to filter them with a filter as both of the liquid will pass through it.
For a mixture of a solid and a liquid (for example sand and water) it can be easily separated through a filter as on filtration solid will be left on the filter and the liquid will pass through it.
For a mixture of two miscible liquids (for example milk and water) both of them will form a single identity, and on filtration both of them will pass through the filter. Hence it is not possible to separate them through filter.
For a mixture of liquid and gas (for example drinking soda or Pepsi) filter is not needed for their separation as it will be separated when exposed in air.
