The correct answer is option 1: NaCl. Brine is an aqueous solution that contains a high concentration of salt. In this case, the salt referred to is sodium chloride (NaCl).
Option 2, NaOH, refers to sodium hydroxide, which is a strong base and not commonly used in brine solutions.
Option 3, NaHCO3, refers to sodium bicarbonate, also known as baking soda. While it can be dissolved in water to form a solution, it is not typically referred to as brine.
Option 4, Na2CO3, refers to sodium carbonate, a commonly used chemical in many industries. However, it is not typically used in the formation of brine.
Therefore, the correct answer is NaCl, as it is the main component of brine solutions. It is important to note that brine solutions can vary in concentration and may contain other dissolved substances, but the presence of sodium chloride is what defines it as brine.