Dolorous means showing sorrow or pain. If you knew that dolor means pain in Spanish and douleur means the same in French, you might have been able to get a sense of the words's meaning, even if you did not know exactly what it meant. You're looking for an answer meaning something good, like happy or joyful. Blithe means happy and carefree, so that works best of all the answer choices.
If you guessed and you knew dolorous was a negative word, you would have known the right answer had to be positive. Confounded is negative and innocuous is neutral, so they could be eliminated.
