We have to find how the interval (1-α) affects the width of the confidence interval.
The interval (1-α) represents the confidence required for the interval.
The greater the confidence required, the wider will be the interval.
This means also that when we decrease the confidence required, the interval width decrease too, as we are less strict with the number of sample means that have to fall within that interval.
Then, when (1-α) decreases, the width of the confidence interval also decreases.
Answer: A. Decreased,