工程担保中最重要的、担保金额最大的一种工程担保是( )。

A．投标担保
B．履约担保
C．预付款担保
D．分包担保

An analyst identifies the following cash flows for an average-risk project: Year 0 - $ 5000 Years 1-2 $ 1900 Year 3 $ 2500 Year 4 $ 2000 The project’s discounted payback period if the company’s cost of capital is 12% , and internal rate of return of the project, are closest to: Discounted payback periodIRR （）

A. 3.0 years           13.3%

B. 3.0 years           23.2%

C. 3.9 years           13.3%