For the purposes of this Act and of any regulations or byelaws made under this Act—
(a)any article commonly used for human consumption shall, if sold or offered, exposed or kept for sale, be presumed, until the contrary is proved, to have been sold or, as the case may be, to have been or to be intended for sale, for human consumption ;
(b)any article commonly used for human consumption which is found on premises used for the preparation, storage, or sale of that article and any article commonly used in the manufacture of products for human consumption which is found on premises used for the preparation, storage or sale of those products, shall be presumed, until the contrary is proved, to be intended for sale, or for manufacturing products for sale, for human consumption ;
(c)any substance capable of being used in the composition or preparation of any article commonly used for human consumption which is found on premises on which that article is prepared shall, until the contrary is proved, be presumed to be intended for such use.