Exploration of antarctica’s interior did not begin until a treaty was signed by 12 nations airplanes were strong enough to withstand the winds and cold sailors from european countries landed on pack ice tractors were brought to the continents

The answer is "airplanes were strong enough to withstand the winds and cold ".

Explanation:

the end of the gilded age coincided with the panic of 1893, a deep depression, which lasted until 1897 and marked a major political realignment in the election of 1896. this productive but divisive era was followed by the progressive era.