Perfectly competitive markets are economically efficient in the long run, partly because Select one: a. entry barriers enable such firms to invest in high-return capital projects. b. firms in these industries produce an output where the price is equal to the minimum average variable cost. c. the price consumers are willing to pay for the last unit just equals the cost of having to produce that additional unit. d. entry and exit guarantees a positive long-run profit above average total cost for each firm.

The business cycle is the periodic but irregular up-and-down movement in economic activity, measured by fluctuations in real gross domestic product (gdp) and other macroeconomic variables. a business cycle is typically characterized by four phases—recession, recovery, growth, and decline—that repeat themselves over time. economists note, however, that complete business cycles vary in length. the duration of business cycles can be anywhere from about two to twelve years, with most cycles averaging six years in length. some business analysts use the business cycle model and terminology to study and explain fluctuations in business inventory and other individual elements of corporate operations. but the term "business cycle" is still primarily associated with larger (industry-wide, regional, national, or even international) business trends.

Hello! i️ believe a.) is the correct answer. : )