"Bean curd with brine" means that in the process of making bean curd, protein granules in beans are gathered together with brine to form bean curd brain, and then bean curd is formed. The chemical substances of salt white used for bittern lighting are mainly:

A. magnesium chloride

B. copper sulfate

C. sodium nitrate

D. calcium carbonate

Correct answer: a

analysis

The first step is to test the common sense of life.

In the second step, the scientific name of brine is bittern, which is the mother liquor left in the salt pond after making salt from seawater or salt lake water. The main components are magnesium chloride, calcium sulfate, calcium chloride and sodium chloride, and it tastes bitter. Magnesium chloride crystals separated after evaporation and cooling, called halogen blocks, are commonly used as coagulants for making tofu in northern China, which can coagulate protein in soybean milk into gel and analyze the water. Tofu made of bittern as coagulant has strong hardness, elasticity and toughness, and is called old tofu, or north tofu and hard tofu.