My choice is (A) O o o = comf'ta'ble.
Choice (D) o o O o produces a non-English sounding word as the third syllable in com'for'ta'ble is pronounced with a reduced vowel and reduced vowels do not carry primary stress.
Note that, there are two ways to pronounce comfortable:
 comf-ta-ble <3 syllables>
 com-fr-ta-ble <4 syllables>
Student or Learner