Final answer:
Thiamine deficiency is the probable cause of alcohol-induced amnestic disorder.
Step-by-step explanation:
The probable cause of alcohol-induced amnestic disorder is thiamine deficiency (option a). Thiamine (vitamin B1) is an essential nutrient that is required for the normal functioning of the brain. Alcohol interferes with the absorption and metabolism of thiamine, leading to a deficiency. This deficiency can result in neurological symptoms, including memory impairment, which is characteristic of amnestic disorder.