11. Rockets in interplanetary space: A. work by first emitting a cloud of hot gases against which they can then push; rockets taking off from the Earth push against the ground itself B. 'push against' the interplanetary medium (relying on the fact that space is not a perfect vacuum) C. rely on the conservation of linear momentum: they will move forward whenever particularly energetic (i.e. extremely hot) material is thrown out the back D. rely on the conservation oflinear momentum: they will move forward whenever material of any sort is thrown out the back