Syngamy, also known as fertilization, refers to the fusion of two gametes to form a zygote. The correct answer is option 2, which states that syngamy results in the formation of a diploid zygote.

Option 1 suggests that syngamy results in the formation of a haploid zygote, which is incorrect. Syngamy involves the fusion of two haploid gametes to produce a diploid zygote.

Option 3 suggests that syngamy results in the formation of non-motile male gametes. However, syngamy is the fusion of two gametes, typically a motile sperm and a non-motile egg, rather than the formation of gametes.

Option 4 suggests that syngamy results in the formation of motile male gametes, which is also incorrect. Gametes are the reproductive cells that fuse during syngamy, and they are typically produced by specialized tissues or organs, not directly through syngamy itself.

Therefore, the correct answer is option 2, as syngamy indeed results in the formation of a diploid zygote.