The correct answer is option 1: citing another use of the same product. Evergreening of patents refers to the practice of extending the exclusivity of a patent beyond its original term. Option 1 specifically mentions citing another use of the same product, which means that the patent holder claims that their product has a new and different use, even though it may be essentially the same product.

Option 2, citing another process of forming the same product, is not related to evergreening of patents. It refers to a different kind of invention or innovation in the manufacturing process of a product.

Option 3, applying for an extension of patent term, can be a part of the strategies used in evergreening patents. However, it is not the only way to achieve evergreening. Option 1 is a more direct and common approach.

Option 4, citing another product with the same use, is also not a part of evergreening of patents. Evergreening typically involves claiming a different use for the same product, rather than claiming a different product altogether.

In summary, evergreening of patents is commonly achieved by citing another use of the same product, which makes option 1 the correct answer.