Assuming Everything Else Is Constant,when a Stock Goes Ex-Rights the Stock

Assuming everything else is constant,when a stock goes ex-rights the stock price should:

A) decrease since the stockholder is losing an option.
B) increase since the corporation no longer has the right to force the stockholder to convert.
C) remain the same since an efficient market would anticipate this change.
D) remain constant as shareholder value is unaffected by a rights offering.
E) decrease by the amount of the tax applicable to the right.