A vessel at 1000 K contains $CO_2$ with a pressure of 0.5 atm. Some of the $CO_2$ is converted into $CO$ on the addition of graphite. If the total pressure at equilibrium is 0.8 atm, the value of $K$ is

Question

( A ) 1.8 atm
( B ) 0.3 atm
( C ) 3 atm
( D ) 0.18 atm