Introduction:
Russia is a vast country with a diverse industrial landscape. Several cities in Russia have emerged as prominent industrial areas, contributing significantly to the country's economy. Two such cities are Moscow and St. Petersburg.

Moscow:
- Moscow, the capital city of Russia, is one of the most important industrial centers in the country.
- It is home to a wide range of industries such as manufacturing, construction, aerospace, automotive, electronics, and information technology.
- The city has a well-developed transportation infrastructure, including an extensive network of roads, railways, and airports, which facilitates the movement of goods and materials.
- Moscow also has a large labor force and a high concentration of skilled professionals, making it an attractive destination for industrial investment.

St. Petersburg:
- St. Petersburg, the second-largest city in Russia, is another significant industrial area.
- The city has a long history of industrial development and is known for its manufacturing industries, including machinery, metalworking, shipbuilding, and chemical production.
- St. Petersburg is strategically located on the Baltic Sea, providing easy access to international markets and facilitating trade.
- The city's industrial sector has been supported by the presence of several research institutes, universities, and technical schools, which contribute to the development of new technologies and skilled workforce.

Petrograd:
- Petrograd, formerly known as St. Petersburg, was the capital of the Russian Empire before the Russian Revolution.
- During that time, it was a major industrial center, with a focus on heavy industries such as iron and steel production, machinery manufacturing, and textile production.
- However, after the Russian Revolution, the city was renamed Leningrad and experienced significant changes in its industrial landscape.

Both (a) and (b):
- The correct answer to the question is option 'D' because both Moscow and St. Petersburg are prominent industrial areas in Russia.
- These cities have a diverse range of industries and contribute significantly to the country's economy.
- They have well-developed infrastructure, skilled labor force, and favorable business environment, attracting industrial investment.

Conclusion:
Moscow and St. Petersburg are two prominent industrial areas in Russia. These cities have a rich industrial history and continue to thrive as important economic hubs. They offer a wide range of industries, excellent infrastructure, and skilled labor force, making them attractive destinations for industrial investment.