Research on the Cause of Alzheimer's Disease Has Led to the Conclusion

Research on the cause of Alzheimer's disease has led to the conclusion that:

A) the hereditary component explains the onset of the disease.
B) at least five different chromosomes have been found to be related to Alzheimer's disease.
C) there appears to be a significant hereditary component, but this does not fully explain its onset.
D) there is little or no evidence of a genetic component to Alzheimer's disease, but there may be a viral cause.