Yes it is, it has a period therefore a complete sentence.
Answer:
The teacher begins with a sentence, for example 'If I go out tonight, I’ll go to the cinema.' The next person in the circle must use the end of the previous sentence to begin their own sentence, for example 'If I go to the cinema, I’ll watch Charlie and the Chocolate Factory.' The next person could say, 'If I watch Charlie and the Chocolate Factory, I’ll eat lots of chocolate.' Then, 'If I eat lots of chocolate, I’ll put on weight.' etc.
Dickens, Charles. Great Expectations. New York: Dodd, Mead, 1942. Print.
Structure: Last, First M. Book. City: Publisher, Year Published. Print.