What do astronomers mean when they say the universe is expanding?.

it will be pushed away from the source of the electric field. a negative charge in a cloud induces a positive charge in the ground below the cloud.

explanation:

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.

b.transmitters send radio waves, and receivers capture radio waves.

there are no components of a physical goal mentioned on the list of choices that you've provided.