Answer:
C. The inability to sleep normally.
Step-by-step explanation:
Insomnia is a sleeping disorder when a person is unable to sleep normally. It is also a medical condition that makes a person unable to get enough sleep or wake up every now and then.
In the given scenario, "Michael struggled with insomnia." This means that Michael can't stay asleep and would wake up every 30 minutes. These are signs of a sleeping disorder, which suggests the inability to stay asleep for a longer duration or even get enough sleep.
Thus, the correct answer is option C.