Final answer:
The word that has a similar relationship as 'ominous:disaster' is (a) auspicious:success.
Step-by-step explanation:
The word 'ominous' is a word used to describe something that gives the feeling that something bad or unpleasant is going to happen. In the given options, the word that has a similar relationship as 'ominous:disaster' is (a) auspicious:success. 'Auspicious' means conducive to success or favorable.