They do not have a distinct head and thorax but a fused version of the two called a cephalothorax. That's one of the major differences between insects and crustaceans, both being subgroups of arthropods.
The correct answer of the given question above would be option D. The hypothalamus is involved in sleep as a response to decreasing light, the hypothalamus suprachiastmatic nucleus causes the pineal gland to increase production of melatonin. The hormone melatonin is responsible for maintaining the circadian rhythm of the body.
The end result of cytokinesis is another cell cycle because it already is the final stage of a cell cycle.
Decrease because they become compacted due to the process of compaction and cementation brought about by the heat and pressure.
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