Function of Fine Aggregate:
Fine aggregate is an essential component of concrete and is commonly known as sand. Its primary function is to assist in producing workability and uniformity in the mixture. However, it also plays a crucial role in other aspects of concrete production. The correct answer to the given question is option 'D', which states that the function of fine aggregate includes all of the above.

Assisting in Workability and Uniformity:
The presence of fine aggregate in the concrete mixture helps to improve its workability. Workability refers to the ease with which the concrete can be mixed, placed, and finished. Fine aggregate particles fill the voids between the coarse aggregate particles, reducing the friction and making the mixture more flowable. This improved workability allows for easier concrete placement and compaction.

Furthermore, fine aggregate also contributes to the uniformity of the concrete mixture. It helps to distribute the cement paste evenly throughout the mixture, ensuring that each particle of coarse aggregate is coated with the paste. This uniform distribution improves the overall strength and durability of the hardened concrete.

Assisting Cement Paste Suspension:
The cement paste acts as the binder in the concrete mixture, holding all the other ingredients together. Fine aggregate plays a crucial role in assisting the cement paste to hold the coarse aggregate particles in suspension. The smaller size of the fine aggregate particles allows them to fill the gaps between the larger coarse aggregate particles. This filling effect helps to prevent the segregation and settling of the coarse aggregate, ensuring that it remains uniformly distributed throughout the mixture.

Promoting Plasticity and Preventing Segregation:
Plasticity refers to the ability of the concrete to be molded and shaped without cracking. The presence of fine aggregate promotes plasticity in the mixture by providing a lubricating effect between the particles. This lubrication reduces the internal friction and allows the concrete to be easily molded and compacted.

Additionally, fine aggregate helps to prevent the possible segregation of the cement paste and coarse aggregate. Segregation occurs when the different components of the concrete separate from each other, resulting in an uneven distribution. The fine aggregate particles act as a filler and help to prevent the settling of the heavier coarse aggregate particles, ensuring a homogeneous mixture.

Conclusion:
In summary, the function of fine aggregate in concrete production is multi-fold. It assists in producing workability and uniformity in the mixture, promotes plasticity, and prevents possible segregation of the cement paste and coarse aggregate. These functions are vital for achieving a high-quality and durable concrete mix.