During a filtration process, losing some liquid when filtering occurs because:

The reason some liquid is lost during a filtration process is that some liquid inevitably remains with the solid material after the filtration has taken place. When a mixture is poured through filter paper, the solid particles are trapped in the filter while the liquid passes through. However, not all of the liquid can be separated completely from the solid particles—some is retained on the surface of the solids or within their structure. This is why there is a small amount of liquid that does not make it through the filter, leading to the loss of volume in the filtrate.

Other choices do not accurately explain the phenomenon: filter paper doesn't absorb all liquid to the extent of causing significant loss, vacuum filtration is a method that can improve efficiency but does not eliminate the retention of liquid, and while filtering can generate some heat due to friction, it is not a reason for liquid loss in the process.