The correct answer is option 'C', Decline.

Explanation:
The product life cycle consists of various stages that a product goes through from its introduction to its decline. These stages include introduction, growth, maturity, and decline. In the decline stage, the company takes a decision whether to maintain, harvest, or drop the product. Let's understand this in detail:

1. Introduction Stage:
- This is the first stage of the product life cycle where the product is introduced in the market.
- During this stage, the product is launched, and the company incurs high costs on marketing and promotion to create awareness and build a customer base.
- Sales are typically low, and the company may not be generating profits.

2. Growth Stage:
- In this stage, the product starts gaining acceptance in the market, and sales increase rapidly.
- Customers become aware of the product's benefits, and market share starts growing.
- The company invests in expanding production capacity and distribution channels to meet the increasing demand.
- Competitors may enter the market, leading to increased competition.

3. Maturity Stage:
- The maturity stage is characterized by stable sales and market saturation.
- During this stage, the product has a large customer base, and competition intensifies.
- Price wars and aggressive marketing strategies are common to maintain market share.
- The company focuses on product differentiation, improving quality, and customer service to stay competitive.
- Profit margins may start declining due to increased competition and price pressure.

4. Decline Stage:
- The decline stage is the final stage of the product life cycle, where sales start declining.
- This can happen due to various reasons such as technological advancements, changing customer preferences, or the emergence of substitute products.
- In this stage, the company needs to make a decision regarding the future of the product.
- The options available are:
a) Maintain: The company can continue to invest in the product by making improvements or targeting niche markets to extend its life cycle.
b) Harvest: The company can reduce marketing and investment in the product and focus on maximizing profits from existing sales.
c) Drop: The company can decide to discontinue the product and allocate resources to other products or ventures.

In conclusion, the decline stage of the product life cycle is where the company takes a decision whether to maintain, harvest, or drop the product based on its market performance and future prospects.