Tundra soils are generally frozen and are categorized as Gelisols. And in order to be a Gelisol, permafrost must be within 100cm of the soil surface.
D is the best answer. Hope this helped :)
Explanation:
Robins are born in the spring or summer and are mature birds and ready to breed in the following spring or summer. They do not mate for life. Pairs usually remain together during an entire breeding season, which can involve two or three nestings. However, in spring, sometimes a male and female who mated the previous year will both return to the same territory and end up together for another year. This happens most frequently when they were successful raising babies the previous year. Robins lay one egg per day, for a total of 5–6 eggs in a clutch. The eggs hatch about 12 - 14 days after the last egg was laid. Baby robins jump from their nest when they are about 13 days old, but the range is 9 - 16 days. After leaving the nest (fledging), it takes another 10-15 days for babies to become strong fliers and independent birds. The parents continue to feed their young during this period.
Most robins die their first year. But the lifespan goes up dramatically for the ones that survive this critical time, because they've learned so many important life skills. Of those that survive their first year, most wild robins live to be about 5 or 6. As of February, 2001, the longest-living banded wild robin ever recorded had survived 13 years and 11 months, according to the Bird Banding Laboratory at the Patuxent Wildlife Research Center. In captivity, robins have survived longer than 17 years.
It will result in growth overshoot of bear and the population will exceeds the habitat's carrying capacity.
The fishes serves as food for bears in the food chain of the ecosystem (river). The abundance of fish means there is more and enough food for bears, which in turns enhance their growth and reproduction (exponential phase).
However, bears population will continue to increase (overpopulation) and the carrying capacity (i.e., the amount of resources an habitat can provide for its inhabitants) is depleted. Thus, competition, predation, disease outbreak and others, would set in, resulting to loss of species and habitat in the long run.
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