Please find the mistakes and write down the correct sentences. 1.european explorers crossed the atlantic ocean before the 15th century. 2. they knew a lot about the atlantic ocean. 3. columbus saw america for the first time on the 10th of october, 1492. 4. it took him 5 months to cross the atlantic ocean. 5.they had very fast ships. 6.we celebrate columbus day on the 14th october.