IF I ________, I WOULD HAVE CALLED YOU.a.HAVE NOTICEDb.NOTICEDc.HAS NOTICEDd.HAD NOTICED

To determine the correct option for the sentence "IF I ________, I WOULD HAVE CALLED YOU," we need to analyze the context and the grammar of conditional sentences.

Breakdown of the Options

1. a. HAVE NOTICED - This form is not grammatically correct in the conditional construction.
2. b. NOTICED - This is the simple past form, which is not appropriate for this type of conditional.
3. c. HAS NOTICED - This is present perfect and does not fit in the context of a past unreal condition.
4. d. HAD NOTICED - This is the correct choice as it is the past perfect form, which is appropriate for expressing an unreal condition in the past.

Conclusion

The correct option is d. HAD NOTICED.

Thus, the complete sentence reads: "IF I HAD NOTICED, I WOULD HAVE CALLED YOU." This indicates that the speaker did not notice something in the past and, as a result, did not call.