What cause the earth to habe seasons ?

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answer: collecting information/data

reason: the student is going around and asking people questions to collect data

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answer( increase) their individual contractile activity;

answer: d. load

a river's load refers to the natural phenomena in which the sediments, rocks   stones, boulders and other deposits are removed and picked from the bottom bed of the river due to the abrasion resulted by the high speed water current.