A、是A。
B、是B。
C、是C。
D、是D。

单项选择题Diamond Ltd has a payback period limit of three years and is considering investing in Project Alpha . The project requires an initial investment of ) 1 250,000 2 250,000 3 400,000 4 300,000 5 200,000 6 50,000 The company's cost of capital is 10%. What is the discounted payback period of Project Alpha? A、 Between 1 and 2 years B、Between 3 and 4 years C、Between 4 and 5 years D、Between 5 and 6 years

单项选择题若是欧氏空间的标准正交基，则下列向量组还是标准正交基的是（ ）。