Why is this not an isomer of hexane?

BEZ IT THE structure of the HEXANE ITSELF

OTHERS R THE ISOMER OF THIS STRUCTURE.

AND THIS STRUCTURE DON'T CONTAIN A CARBON WITH LESS THAN 2 HYDROGEN ATOMS WHICH R COMPULSORY FOR A STRUCTURE TO BE A ISOMER

answer; /// i do believe that the correct answer is (c)nuclear bond

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )