Final answer:
The correct statement that indicates an understanding of insulin glargine (Lantus) is that there is no peak time for Lantus.
Step-by-step explanation:
The correct statement by a patient with diabetes mellitus that indicates an understanding of the medication insulin glargine (Lantus) is 'D. There is no peak time for Lantus.' Insulin glargine is a long-acting type of insulin that is used to control blood sugar levels throughout the day. Unlike other types of insulin, Lantus has a relatively constant level of activity and does not have a distinct peak time.