Which type of will is valid only if it is written in the handwriting of the testator?

The correct choice is the holographic will. A holographic will is a type of will that is entirely handwritten and signed by the testator, meaning the person who is making the will. For a holographic will to be considered valid, it must meet specific criteria, including that the material provisions are written in the testator's own handwriting. This form of will does not necessarily require witnesses or formalities that are commonly needed for other types of wills, such as formal wills or attested wills.

In contrast, formal wills usually require specific legal procedures, including the presence of witnesses who attest to the validity of the document. Attested wills also need to be signed by the testator and by witnesses who sign in the presence of one another and the testator. Statutory wills are standardized forms established by state law that must adhere to certain regulations. Holographic wills provide a more flexible option for individuals who wish to create a will without the involvement of legal counsel or formal procedures, emphasizing the personal expression of the testator through their handwriting.