I'm not so sure, but I think it's C.
Answer:
The chromatin undergoes further condensation to form the chromosome. ... A chromatid is either of the two strands of a replicated chromosome. Chromatids connected by a centromere are called sister chromatids
Explanation:
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C. He could suffocate from lack of oxygen in his blood.
Given the statement that hemoglobin (used to transport oxygen throughout our body) is more attracted to carbon monoxide, it is highly likely that most, if not all, the hemoglobin in a human body will be bound to carbon monoxide instead of oxygen when a person inhales too much carbon monoxide. This results in a lack of hemoglobin carrying oxygen to the cells of the body. Oxygen deficiency occurs.
C. Desert
A. The tilt of the Earth's axis as it circles the Sun.