The answer is C. nitrogen.
Plants are main producers in ecosystems so, primary productivity of ecosystems depends on them. Carbon is necessary for plants, but it is widely present in plants. On the other hand, calcium and sodium are not as essential. However, nitrogen is important for plants because it is necessary to make proteins. Proteins take part in many different processes such as photosynthesis (this is actually primary productivity). But, nitrogen is not available to plants, they cannot absorb it simply from the air but rely on some symbiotic bacteria which are able to.
Answer:
Cervix.
Explanation:
The process of the child birth and the delivery of the baby from the mother's womb shows the labor. The labor process is completely divided into the four stages.
The passageway is the first stage of labor. This is further divided into the early labor and active labor. The vagina and cervix are the main component of the first phase and consist of the soft tissue. The birth canal is formed by the together of the vagina and cervix.
Thus, the answer is cervix.
It is d because the law was passed around 1976 I am not sure but this is the best estimate
