Answer:
Explanation:
Stem cells are cells with the potential to develop into many different types of cells in the body. They serve as a repair system for the body.
Some of the organisms have evolved in such a way that they remain inactive when the predator populations are active.
Adaptive theory of sleep suggests that the prey population prefer to sleep when (in this case, at night) the predators are most active. The prey population use this time in taking rest and restoring energy for other works. As the prey population is inactive and remained protected in safe places, they are less likely to be predated.
Hence, the correct answer is adaptive theory of sleeping.
After 10 years, the isotope would have had two half lives. For each half life, half of the material reacts. Therefore, after one half life, 50% remains. Then, after a second, 25% remains. D is the correct answer.
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The correct answer is: The speed of sound is faster in the water than in the air.
The speed of sound is different between those two mediums because they have different densities. Since, water is denser than air, more energy is required to generate a wave but once it stars, it travels faster than it would do in air. Sound waves’ travel can be presented by particles that transmit the energy one to another as they bump. The sound speed is lower in the air (than in water) because particles are far apart, so they travel further before they collide.