Specialized structures that recognize neurotransmitter molecules and, when activated, may cause a change in the electrical activity of the neuron, are called

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explanation:

what's the

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

a covalent bond, specfically triple bond