The figure given above shows the growth of pollen tube. Observe the figure and answer the following question.

Triple fusion takes place when:

One male gamete fuses with the polar nuclei 

The correct answer is Option (4) → One male gamete fuses with the polar nuclei

After the pollen tube enters one of the synergids in the embryo sac, it releases two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus, resulting in syngamy or the fusion of two haploid nuclei. This fusion gives rise to a diploid cell called the zygote,  which will develop into an embryo.

The other male gamete moves towards the central cell, which contains two polar nuclei. The male gamete fuses with the polar nuclei, leading to the fusion of three haploid nuclei. This fusion event is known as triple fusion. It results in the formation of a triploid primary endosperm nucleus (PEN).