Who were the first people to reach the north pole? a. robert edwin peary, matthew henson and four inuits, in 1909 b. roald amundsen's party c. a swedish expedition reached it by air balloon in 1897 d. robert falcon scott and ernest shakleton

There are two people who claimed to be the first to reach the north pole - Robert Edwin Peary and his employee Matthew Henson and four Inuit men Ootah, Seegloo, Egingway, and Ooqueah on April 6, 1909, and Frederick Cook, accompanied by two Inuit men, Ahwelah and Etukishook, on April 21, 1908. Neither claim is widely accepted today - both men likely got close but not to the exact north pole.

Soviet pilot Ivan Cherevichnyy was the first person to undisputedly reach the North Pole when he landed his plane there on April 23, 1948.

Hope this helps!

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

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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