आर.एफ. हॅरॉडने त्याच्या आर्थिक विकासाच्या प्रतिमानासाठी खालीलपैकी कोणत्या विकास दराच्या वेगवेगळ्या संकल्पना वापरल्या आहेत ?
a. वास्तविक वाढीचा दर
b. हमी वाढीचा दर
c. वार्षिक वाढीचा दर
d. नैसर्गिक वाढीचा दर

The correct answer is Option C (a, b and d).

Key Points:
• Harrod-Domar Growth Model: Developed independently by Roy F. Harrod and Evsey Domar, this macroeconomic model explains an economy's growth rate in terms of the level of saving and productivity of capital.
• R.F. Harrod's Three Rates of Growth: To explain the dynamic process of growth and the difficulty of maintaining steady equilibrium, Harrod introduced three distinct concepts of growth rates:
• 1. Actual Rate of Growth (G): The rate of increase in income that is actually achieved in reality, determined by actual savings and investment (represented by G = s/c). (Statement 'a')
• 2. Warranted Rate of Growth (G_w): The full-capacity rate of growth, or the rate of income growth required to keep investors fully satisfied that they have produced the exact right amount of capital. It is the steady-state equilibrium. (Statement 'b')
• 3. Natural Rate of Growth (G_n): The maximum possible growth rate allowed by macro factors like population growth (labor force) and technological progress. (Statement 'd')
• Annual Rate of Growth (c): This is a generic statistical term and is *not* a theoretical concept used in Harrod's model.
• Conclusion: Harrod used Actual, Warranted, and Natural rates of growth.
• Key Takeaway: Harrod's model uses three specific growth rates: Actual (G), Warranted (G_w), and Natural (G_n).