The question -a single muscle cell can contain dozens of nuclei. which stage of the cell cycle is the cell not completing? how do you know?

I do not understand your question fully because there might be some context missing to it:

Having more nuclei is not something caused by the lack of a process or stage. Some muscle cells usually fuse together, which means they become one. But before they became one, each had their own nuclei. And when they fused, each one kept their nuclei, making one cell with more than one nuclei.

Those cells are called multinucleated cells.

Hope it helped,

BioTeacher101

a few examples of ethical concerns involving genetically engineering of humans include

-privacy of genetically tested people

- potential side effects

-long term effects

common management practices in dairy and poultry farming are: (i) proper shelter facilities and their regular cleaning. (ii) some basic hygienic conditions such as clean water, nutritious food, etc. (iii) animals are kept in spacious, airy, and ventilated place.