Why might several competing corporations join together in an association?

because there is often strength in numbers

because they often have common issues that may affect an entire industry

because they can all benefit from governmental policies

all the above

The best answer to the question: Why might several competing corporations join together in an association, would be: All of the above.

Explanation:

As the popular addage says, there is strength in numbers. The reason for the last option being the best answer is that competing corporations may join together in an association because they find common ground that instead of separating them more, benefits them, if they put up a gathered front. Most commonly, this comes when there is a desire to push for legislation that will benefit the interests of one, and all, the members of the association. Just as laborers join in unions to find benefits in the power of numbers, and their lobbying power in Congress, because numbers mean higher representation, so do corporations, even those competing. Also, even competitors find that there are common problems that affect them all in a specific industry, and when they join together, there is more power to what they can do as one front, rather than one single company, regardless of how big it might be, to influence policy-making.