As the US increased the production of natural gas

As the US increased the production of natural gas released from underground shale formations, creating more output of polyethylene, it was expected that makers of plastic products such as plastic trash bags, toys, containers etc., which use polyethylene as a raw material, would benefit from the same as a result of the decrease in the price of natural gas. However, makers of plastic products have instead reported no cost benefit as a result of the increase in the supply of natural gas.

Which of the following, if true, most explains the zero cost benefit as reported by the makers of plastic products mentioned in the above argument?

A: To discourage people from using plastic products, many countries have started levying heavy taxes on the plastic industry as a measure to increase the cost of production and the resultant price of plastic products.

B: The price of ethane, a component of natural gas and raw material for polyethylene has decreased due to the increased supply of natural gas.

C: The makers of polyethylene have increased their profit margins and hence are not passing on lower cost benefits to their customers.

D: It is predicted that plastic manufacturers will eventually realize cost benefits, once the production of natural gas is further ramped up.

E: Since the production of natural gas released from shale formation has increased, the demand for plastic products has decreased significantly.

Explanations please... Thanks