三个选项的回购有什么区别啊？

问题如下：

If a company’s objective is to support its stock price in the event of a market downturn, it would be advised to authorize:

选项：

A.

an open market share repurchase plan to be executed over the next five years.

B.

a tender offer share repurchase at a fixed price effective in 30 days.

C.

a Dutch auction tender offer effective in 30 days.

解释：

Of the three methods, only an authorized open market share repurchase plan allows the company the flexibility to time share repurchases to coincide with share price declines.