Which of the following identifies two technological advancements during the dawn of the space age between 1951 and 1959?
a. the first successful orbiting satellite was launched by the soviet union, and several space craft launches in the advancement of space exploration.
b. the first human was sent into space, and water was discovered on mars.
c. numerous spacecraft launches resulted in technological advancements, and humans landed on the moon.
d. robotic spacecrafts were sent to gather information about halley’s comet, and the twin voyagers gathered data from distant planets.

Letter A. The first successful orbital satellite was launched by the Soviet Union and several spacecraft launches helped advance space exploration.

Explanation:

Between 1951 and 1959, Sputnik 1 was the first artificial satellite on Earth. It was launched by the Soviet Union on October 4, 1957, at the Soviet Union Nebula Testing Unit currently known as the Baikonur Cosmodrome. In addition, there were other spacecraft launches that advanced space exploration, such as Sputnik 2, launched in space on November 3, conquering the feat of sending the first living creature into space, a dog named Laika.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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