Question

The color contrast between the open ocean and the lagoon between the spit and the mainland. The greater concentration of suspended sediments in the lagoon gives the waters a more turbid appearance. The source of sediment in the lagoon is (are)
[(rivers and streams from the mainland)
(wind-borne sediment from the spit)
(ocean waves washing over the spit)
(all of these contribute)].

Answer 1

The correct answer is - all of these contributed.

The sediments in the lagoons come from multiple different sources. The rivers and streams from the mainland, the sediments brought by the wind, and even the ocean waves that manage to get over the spit occasionally.

The biggest influence in the deposition of the sediments in the lagoons though is by the rivers and the streams from the mainland. They carry sediments with them constantly, and the amount of those sediments is also on a high level, in fact they bring in so much sediments that they have actually built the lagoon itself.

The wind and the ocean waves that manage to get over the spit have much lesser influence in the total deposition of sediments, but still they do in some part, and it shouldn't be put aside.

The combination of the three different sources, with different types of sediments brought to the lagoon by each of them, gives the lagoons a beautiful and unique appearance.