A mixed economy means that part of an economy is managed by the government while part of it is left with the free market.
Its development factors involve allowing private enterprise to run most of the business and then in the later part government can come in for providing public services or regulation of private business etc.
Any number of interest groups.
Answer is C.
The Allied Powers during World War I included the United States, United Kingdom, Serbia, Russia, Italy, France, and Belgium. This means your answer would be 'A.'