Answer: For the given sentence, "It will be fortunate that you were able to fix the faucet because we need to use the water", the correction is given in option (d).
In all other options, the verb tenses in first and second verb don't match.
Explanation: The given sentence says "It will be fortunate that you were able to fix the faucet because we need to use the water"
The first part of the sentence says "will be fortunate" = FUTURE TENSE
then it says "were able to fix" = PAST TENSE
"we need to use water" = PRESENT TENSE (FOCUS ON THIS PART)
In the options for correction that follow, they have not included the 3rd part of the sentence which is in PRESENT TENSE. This proves that the 3rd part is un-changeable and hence the rest of the sentence needs to match it's verb tense. So, converting the entire sentence into present tense for it's verbs, it becomes "It is fortunate that you are able to fix the faucet because we need to use the water"