You have to read the bylaws and shareholders agreements.
As other people said, a stock option is the right to buy stock, not stock itself. Until you exercise the right and buy the stock you probably don't have voting rights, although your companies bylaws may say otherwise.
Every company has it's own bylaws which determine how the company is run. It's not directly based on a percentage of ownership.
For example, at Stack Overflow, there are two kinds of stock: preferred and common. The preferred shareholders own a minority of the stock. They have the right to elect one board member. They also have the right to veto any merger or acquisition. The common shareholders own a majority of the stock. They have the right to elect two board members. The board itself has the right to select the CEO. The CEO actually makes decisions.
In other words: until you read the bylaws and shareholder agreements and understand how a particular company is run, there's no reason to assume that merely owning 51% of the shares of a company gives you control of the company.