6. Complete the sentences:

•His date of birth was _________________________________________________________

•He took part in the expedition of 1647 because ____________________________________

•At that time walrus tusks and whale bones were ___________________________________

•The reason they stopped their mission was ________________________________________

•A Koch is _____________________________________________________________________

•In the northern shores of Asia Dezhnev discovered _________________________________

•Chukchi people used walrus tusks, stones and bones ___________________________

•His discoveries were so great that ________________________________________________