The solution that is optically inactive but chiral with 4 substituents is a meso compound. A meso compound is a molecule with chiral centers but also has an internal plane of symmetry, which results in the overall molecule being optically inactive. This occurs when the substituents on the chiral centers cancel each other out in terms of their effect on the overall molecule's chirality. Therefore, even though the molecule is chiral, it does not rotate plane-polarized light and is optically inactive. **

In a Fischer projection, the substituents to the left represent the groups that are pointing towards the viewer, while the substituents to the right represent the groups that are pointing away from the viewer. This convention helps to visualize the three-dimensional structure of a molecule in a two-dimensional representation. **

The choice between a free market economy and a planned economy depends on the specific goals and values of a society. A free market economy allows for individual freedom and competition, which can lead to innovation and efficiency. However, it can also result in inequality and lack of regulation. On the other hand, a planned economy allows for more control and distribution of resources, but it can stifle individual initiative and innovation. Ultimately, the decision between the two depends on the balance a society seeks between individual freedom and social equality. **

The answer to this question depends on one's perspective and values. A social market economy combines elements of both a free market and government intervention to ensure social welfare and economic stability. It aims to balance individual freedom with social responsibility. On the other hand, a free market economy prioritizes individual freedom and minimal government intervention, allowing for more competition and innovation. Ultimately, the "better" system depends on the specific needs and values of a society, as well as the balance between individual freedom and social welfare that is desired. **

Online commerce refers to the buying and selling of goods and services over the internet, while retail commerce refers to the traditional brick-and-mortar stores where customers can physically visit and make purchases. Online commerce offers the convenience of shopping from anywhere at any time, while retail commerce provides the opportunity for customers to see, touch, and try products before making a purchase. Online commerce often involves lower overhead costs and can reach a wider audience, while retail commerce provides a more personalized and immediate shopping experience. **

A social market economy combines elements of both a free market economy and a planned economy. It allows for private ownership of businesses and resources, while also implementing government regulations to ensure fair competition and social welfare. In contrast, a free market economy relies on minimal government intervention, allowing businesses to operate with little regulation. On the other hand, a planned economy is centrally controlled by the government, with decisions regarding production, distribution, and pricing made by central authorities. **

In a Fischer projection, the substituents that are located to the left are typically the ones with higher priority according to the Cahn-Ingold-Prelog rules, such as groups with higher atomic numbers or multiple bonds. The substituents on the right are usually those with lower priority, like hydrogen atoms or groups with lower atomic numbers. The arrangement of substituents in a Fischer projection helps to determine the stereochemistry of a molecule. **

In a Fischer projection, the substituents on the left side represent the vertical bonds, while the substituents on the right side represent the horizontal bonds. This convention helps to easily identify the stereochemistry of the molecule and determine the relative positions of the substituents. The horizontal bonds on the right side are typically pointing towards the viewer, while the vertical bonds on the left side are pointing away from the viewer. **