Kevin is just learning to walk. He can take a few steps by himself if he uses both hands to hold on to a piece of furniture for support. He can walk to the middle of a room only if one of his parents holds his hands. Which of the following represents the lower limit of Kevin's zone of proximal development (ZPD) for walking?

a. Kevin walking alone by holding onto a piece of furniture with his hands
b. Kevin learning to walk by having his parents hold one of his hands
c. Kevin going back to crawling when he becomes frustrated trying to walk by himself
d. Kevin learning to run after he has mastered walking by himself

a. Kevin walking alone by holding onto a piece of furniture with his hands                                                                          

Explanation:

Zone of proximal development: In psychology, the term "zone of proximal development" is also denoted as ZPD, and was proposed by one of the most influential psychologist named Lev Vygotsky.

According to Lev Vygotsky, ZPD is described as the phenomenon in which the difference between a particular listener's or student's capability to carry out a specific task independently vs. to carry out the task with an elder's or teacher's guidance is being governed.

Explanation:

. Kevin walking alone by holding onto a piece of furniture with his hands

b. Kevin learning to walk by having his parents hold one of his hands

c. Kevin going back to crawling when he becomes frustrated trying to walk by himself

d. Kevin learning to run after he has mastered walking by himself

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).