The period after an initial stimulus when a neuron is not sensitive to another stimulus is the

Absolute refractory period

Explanation:

The absolute refractory period is short in an action potential. During the refractory period, there is no occurrence of another action potential. There would occur two types of refractory periods  

Absolute refractory periods: Absolute period is the period when another action potential won't occur immediately after a first action potential. This refractory period also called an effective refractory period. This period happened because the sodium channel is inactivated and is stable in the same way until the hyper polarization does not occur.  

Relative refractory period:

i think the answer is true : ))

marginal cost is a microeconomic measure that us to evaluate the extent to which the level of production of a good is sustainable in accounting, that is, to how many quantities the company plans to profit from the production of the good.

the concept of marginal cost is simple, it means the cost of producing one more item. for example, in the case of pies, the marginal cost is the cost of producing one more pie than those that have already been produced.

it is important to understand that productive activity influences marginal cost. the marginal cost of some goods can be very high, while others may be insignificant. for example, the marginal cost of producing an extra plane is very high. already the marginal cost of a water company to provide 1l more water is derisory.

in the case of pies, the cost involves the inputs, the labor and the fixed cost, which involves the fixed space of the bakery. the level of production initially has the marginal cost decreasing because there is space and manpower available. however, to produce more you have to hire more workers and buy more inputs. if physical space is limited, workers will conflict with places, inputs and their productivity will decrease, meaning there is an optimum point of production for each level of space and manpower. from this point on, the productivity of the workers will be getting smaller because of lack of space, so that the marginal cost of producing one more pie will be increasing. so, although you have not posted the chart, but if you have the answer, you can see that my explanation goes according to the marginal cost curve that will increase from the 4th pie, answer (c).