$$1\div \left( 2\div 3 \right)\div \left( 3\div 4 \right)\div \left( 4\div 5 \right)\div \left( 5\div 6 \right)$$  $$=1\div 2\times 3\div 3\times 4\div 4\times 5\div 5\times 6$$  $$=1\div 2\times 6$$  $$=3$$．  故选$$\text{A}$$． 
算式$$1\div \left( 2\div 3 \right)\div \left( 3\div 4 \right)\div \left( 4\div 5 \right)\div \left( 5\div 6 \right)$$的结果是． 
Options:
1: $$3$$ 
2: $$6$$ 
3: $$1$$ 
4: $$55$$ 