The given sentence is a statement.
In the indirect speech 'told' may be used for 'said to'.
According
to the rules of narration and reporting, if the reporting verb is in
the past tense, the tense of the reported verb is changed into its
corresponding past form. The reporting verb in the given sentence,
'said', is in the past form. Therefore, the reported verb, 'cannot' will
change into 'could not'. The first person pronoun 'I' will change to third
person 'he'. The second person is changed into the person of the speaker.
Thus, in indirect speech the sentence must be,
George told me that he could not help me.
Thus option C is the correct answer.
Options A,B,D are incorrect as they do not follow the rules of Narration and Reporting.