Explain why the passenger pigeon, which was once the most abundant bird in north America, disappeared completely.

Answer with Explanation:

The "passenger pigeon" used to be North America's most popular bird. Their population even reached 3 billion (or even more). They always traveled together. Their decline in number was noted in the 19th century. People became interested in hunting them for food because they were relatively cheap and tasty . They were also a great source of protein. It was easy to hunt them down although they could fly very fast because their flocks were huge in number. Some people killed them because they didn't want the birds ruining their crops. Their nesting grounds were also disturbed, which ultimately drove them away from the forests. People were overkilling them, and this sped up with the advancement of technology. The number of pigeons killed outnumbered the newborn pigeons, and after decades of hunting them down, their number dwindled with the last one passing away in 1914.

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.  

read more on -

the answer is b.) hydrogen bonds between bases.