Answer:
The answer is between a or b
but I strongly suggest the option a.
Evolution is the answer
That should be the cell membrane. The cell membrane acts as a filter in and out.
1. Sand particles are too big to dissolve so their density sinks them
2. Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles.
Carbon dioxide is transported in the blood in three ways: (i) dissolved in solution; (ii) buffered with water as carbonic acid; (iii) bound to proteins, particularly haemoglobin. Source: https://academic.oup.com/bjaed/article/5/6/207/331369
