The correct option is
C reliable
The given sentence is normally used to report a news item either in the newspaper, television or some other media. The word, 'sources' refers to 'news sources'.
The word, 'intelligent' is an adjective which means '
having or showing intelligence'. There is no intelligence involved in reporting that "the Chief Minister did not consult his cabinet members on this issue'. Hence, this is not the appropriate adjective and option A is incorrect.The word, 'simple' is an adjective which means 'easily understood or done'. This word does not describe the noun, 'sources'. Hence, option B is incorrect.
The word, 'reliable' is an adjective which means 'able to be trusted/ trustworthy'. The source of a news which is to be reported has to be trustworthy. Hence, this is an appropriate adjective which can be used to describe the noun 'sources'. Option C is correct.
The word, 'fundamental' is an adjective which means 'basic/primary'. This does not correctly describe the noun, 'sources'/'news sources'. Hence, option D is incorrect.