While converting a speech from direct to indirect, the tense changes to
past tense (if it is in simple present, it changes to simple past, if
it's in present continuous, it changes to past continuous, and so on.)
because the event is now being spoken of at a later time. When the question is changed to reported speech, the form of the latter is: verb form of 'ask' + question word + clause. (The question form is question word + clause) The given interrogative sentence, when changed to indirect speech must be of this form: He asked + question word (when) + clause (I/he/she intended to make the payment). The verb 'intend' is changed to its past tense 'intended'. The pronoun 'you' is changed to 'I/he/she' because it is not clear whether the quoted "you" is in the first or second person, also, the gender is not clear. This form can be seen in C, hence option C is correct. Option A is incorrect because the tense and form of the verb "intend" has not been changed to past 'intend', but to future tense 'will make', also, 'intend' has been omitted. Option B is incorrect because the verb 'intend' has been removed. Also, the tense has been changed to future continuous tense 'will be making'. Similarly, option D is incorrect: the tense has been changed to past only of the verb 'intended' and not the infinitive 'to make'; the latter has been changed here to continuous tense 'to making'.