In a Certain Hemoglobin Structural Variant,a Deletion in the Coding $\alpha$

In a certain hemoglobin structural variant,a deletion in the coding gene results in a reduction of the production of the beta globin chain.This will result in:

A) decreased quantity of HbA.
B) hemolysis of red blood cells due to unstable hemoglobin.
C) a sickling disorder due to insoluble hemoglobin.
D) an $\alpha$ -thalassemia due to overproduction of alpha-globin chains.