At $300k$ and 1 atmospheric pressure $10ml$ of a hydrocarbon required $55 mL$ of $O_2$ for complete combustion and $40 mL$ of ${CO}_2$ is formed. The formula of the hydrocarbon is

 balanced chemical reaction

$C_x{H}_y+\left(x+\frac{y}{4}\right)O_2\to {xCO}_2+\frac{y}{2}{H}_{2}O$

$10 10\left(x+\frac{y}{4}\right) 10x$

According to the given data = $10\left(x+\frac{y}{4}\right)=55$ ---------------------(I)

10 x=40 ---------------(II)

After solving these two equations we get the value of x =4 and y = 6.

So, the formula of compound  $C_4{H}_6$.

Therefore, option A is correct.