 
			 
			MCQOPTIONS
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				| 1. | If F is a free semigroup on a set S, then the concatenation of two even words is ________ | 
| A. | a semigroup of F | 
| B. | a subgroup of F | 
| C. | monoid of F | 
| D. | cyclic group of F | 
| Answer» C. monoid of F | |