Calcium is important in the synapse because it

A) is necessary for acetylcholine synthesis.
B) signals the exocytosis of the neurotransmitter.
C) binds to receptors on the postsynaptic cell, opening ion channels, and triggering graded potentials.
D) leaves the axon terminal, hyperpolarizing the cell

B) Signals the exocytosis of the neurotransmitter

Explanation:

Calcium ion (Ca2+) channels are critical during the process of neurotransmission; when these channels are blocked, the neurotransmission is inhibited, it happens because the receptors localized in the postsynaptic membrane are not activated

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

answer; i believe that the correct answer is (lung);