The only statement that must be true about Ari's new calipers, compared to his old ones, is:
They are less precise.
Precision refers to the smallest measurement unit that a tool can reliably measure. Since Ari's old calipers can measure down to 0.01 mm and his new calipers can only measure down to 0.1 mm, the new calipers have a larger measurement increment, which makes them less precise.
Regarding accuracy, without information about how well the calipers measure the actual diameter (i.e., whether both calipers give readings that center around the true value), we cannot definitively say whether the new calipers are less accurate or not. Therefore, we cannot conclude that they are less accurate or both less accurate and less precise based solely on the information given.