D both alleles is the answer
When an ecosystem has a scarce nutrient, that is when there is a nutrient limitation.
So the answer is C. <span>Nitrogen is typically the limiting nutrient in freshwater environments.
This is because Nitrogen is the "scarce" nutrient </span>
<span>The probability of an action potential being propagated from neuron to neuron is increased when the postsynaptic neuron's signal is in an excitatory state. During this state, the action potential of a presynaptic neuron increases the probability of transmission of a signal to the postsynaptic neuron.</span>
A hypothesis is considered scientific if it has something that can be supported or refuted through carefully crafted experimentation or observation
