The medium refers to a nutrient matrix prepared by combining different nutrients for the growth and reproduction of microorganisms, plants or animals (or tissues), and generally contains carbohydrates, nitrogen-containing substances, inorganic salts, vitamins, water and other substances . Natural medium is a medium made from animals, plants or microorganisms including their extracts; synthetic medium is a medium prepared according to the composition of natural medium, using chemical substances to simulate synthesis and artificial design; semi-combination medium is It is mainly prepared by chemical reagents, and a medium with a small amount of natural ingredients is also added. According to the above definition, the following are semi-combination media? ['In order to study the growth of chicken embryo cells, a small amount of corn juice is added to a medium of saline amino acid solution.', 'In order to promote the growth of lactic acid bacteria, use the medium made of wheat wort.', 'In order to accelerate the growth of green radix, the medium made of organic components, mineral elements, agar, etc. in the ratio of 3? 1? 2.', 'To observe the production of Clostridium perfringens, add 10 ml of ferrous sulfate medium to 1000 ml of fresh milk.']