What must happen to a chromosome before a cell starts mitosis?

The chromosome must be duplicated before mitosis.

Mitosis is where a parent cell divides and produces 2 genetically indentical daughters cells. This process first requires the parent call to duplicate all of its genetic material. This ensures that the daughters cells are genetically identical to the parent cell and also the other daughter cell.

This is important because mitosis is used in many cases in living things such as growth, repair, and more. This ensures us for example not suddenly changed to another organism or another characteristic.

The answer is d. are all of widely different ages

Even-aged management practices involve those practices necessary to achieve a cohort group of trees. The cohort group of trees includes those trees that are all near the same age. So, to achieve this, trees of widely different ages must be cleared, living only trees that are all near the same age (of the same cohort group).