Which describes a difference between birds and mammals? Birds protect and feed their young
O Birds have nearly hollow bones,
O Birds undergo internal fertilization,
O Birds efficiently transport oxygen to cells,

The soviet union beat the us to the first successful launch, with the october 4, 1957, orbiting of sputnik 1, and later beat the us to have the first human in earth orbit, yuri gagarin, on april 12, 1961. the "race" peaked with the july 20, 1969, us landing of the first humans on the moon with apollo 11