Question

b. The lower courses and the mouths of the Siberian rivers remain frozen throughout the year​

Answer 1

Answer:

Three rivers which flow northwards into the Arctic Ocean — Ob, Yenisey and Lena, have together built this plain. These marshy and swampy lowlands are also called as the Great Siberian plain. The lower courses and mouths of the rivers freeze in winter.

Explanation:

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Answer 2

Answer:

Permanently frozen ground underlies 3,728,900 square miles of Soviet territory, largely in eastern Siberia. Ice is not always present, but temperatures remain below 0° C. to depths down to 890 feet. In some places unfrozen layers are found between frozen ground. Most frozen ground has acquired its low temperature from the atmosphere.