Which of the following are the advantages of plastic over metals? 

1 Plastic is lighter 2. Plastics are usually cheaper 3. Plastics are inert to both acids and alkalis. 

When compared to metals for modern uses, plastic offers advantages in terms of maintenance and adaptability. They are significantly lighter yet providing a similar quality and unyielding character. Utilizing chemical and organic components, plastics are created utilising the polymerization or poly-condensation cycle. They may so easily take on any shape and are versatile. The fact that plastic is lighter than metals and may thus be manufactured into intricate shapes is thus confirmed.

When it comes down to it, heavier materials are more expensive, but plastics are often less expensive since the raw ingredients used to make them, such polythene, are by-products of the oil industry. Metals will typically react quickly with caustic and salt. While plastic will often resist the effects of corrosive bases due to the absence of electrical commerce.

Hence option D is correct.