Buyers of a product will bear the larger part of the tax burden, and sellers will bear a smaller part of the tax burden, when
选项：

A:a. the tax is placed on the sellers of the product.;
B:b. the tax is placed on the buyers of the product.;
C:c. the supply of the product is more elastic than the demand for the product.;
D:d. the demand for the product is more elastic than the supply of the product.