Which process would be difficult for an organism with cell wall?

The answer to this is diffusion. There are instances when you would start to smell the scent of perfume or the awful smell of trash depending on your location, right? This occurs because of diffusion. The scent diffuses towards different directions and that explains why you can smell the scent of perfume even when it was sprayed far away.

This process can be harder when there are cell walls because there are hindrances to the free-flowing movement of the molecules that are being diffused. Take note that it is not only gases that become diffused. Even liquids can diffuse too. The presence of the cell wall may stop or slow down the process.