投资回收期是指：从项目的投建之日起，用项目所得的净收益偿还原始投资所需要的年限。题目描述投资10万，每个月盈利2万，那么回收10万投资需要5个月，而回收期还需要加上投建的时间，因此前6个月实施项目的时间也要加上，因此是11个月。=

The payback period is the time it takes for an investment to generate an amount of income or cash equivalent to the cost of the investment. In this case, the project costs $100,000 and generates $20,000 per month starting from the 7th month.

To calculate the payback period:

1. **Initial Investment**: $100,000
2. **Monthly Benefit**: $20,000

From month 7 onwards, the project generates $20,000 each month. To recover the $100,000 initial investment:

- By the end of month 7, the accumulated benefit is $20,000.
- By the end of month 8, the accumulated benefit is $40,000.
- By the end of month 9, the accumulated benefit is $60,000.
- By the end of month 10, the accumulated benefit is $80,000.
- By the end of month 11, the accumulated benefit is $100,000.

Therefore, the payback period is 11 months. The correct answer is B: 11 months.