If a eukaryotic cell has 20 chromosomes and it undergoes meiosis ii, how many cells will result, and how many chromosomes will they contain?

Four cells and 10 chromosomes each. Before going through meiosis ii it has to go through meiosis i (homologous chromosomes separate) first to form two cells. Then both cells goes through meiosis ii (sister chromatids separate) to form two cells each. Therefore 4 cells.

dissolving power of rain water

Explanation:

The process where the water absorbs CO2  making it a bit acidic so over a period of thousands of years it erodes the limestone

This is correct

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