b
\(\mathop {{C_x}{H_y}}\limits_{10} + \mathop {\left( {x + \frac{y}{4}} \right){O_2}}\limits_{10\left( {x + \frac{y}{4}} \right)} \to \mathop {xC{O_2}}\limits_{10x} + \frac{y}{2}{H_2}O\)
By given data, \(10\left( {x + \frac{y}{4}} \right) = 55....(1)\)
\(10x = 40....(2)\)
\(\therefore x = 4,\,y = 6 \Rightarrow {C_4}{H_6}\)