what is the primary result of a fisson reaction ?

1 conversion of mass to energy
2 conversion of energy to mass
3 binding together of two heavy nuclei
4 binding together of two heavy nuclei

i think its 4, am i right ?

3, and 4 are identical, and wrong.

1 happens, and it is an astounding result. Normally, in commercial applications, it is the primary reason for the reaction.

So all this boils down to what is meant by Primary: Some would say energy, some would say radioactive products, and some would say a mess of lighter nuclei. It would be most unusual for fission to produce just two lighter nuclei, although on animations, it makes drawing it easier. But when a large nuclei "splits", it splits into several messy pieces, some of which split again, and most of the pieces are unstable, and decay into other elements over time.

Actually, the correct answer is option 1: conversion of mass to energy. In a fission reaction, a heavy atomic nucleus, such as uranium-235 or plutonium-239, is split into two smaller nuclei, releasing a large amount of energy in the process. This is due to the conversion of a small fraction of the nuclear mass into energy, as described by Einstein's famous equation E=mc². The released energy can be harnessed for various purposes, such as generating electricity in nuclear power plants. Option 4 ("binding together of two heavy nuclei") is the description of a fusion reaction, where two atomic nuclei combine to form a larger nucleus, releasing energy in the process.