You are the project manager for software development project．The feasibility study can start any time and takes 1 week and requirement gathering takes 2 weeks which can start only after feasibility study．The design and test plan development can start in parallel after the requirements gathering．Test plan preparation takes 8 weeks followed by a review by the customer and the time estimated for review is 1 week．After the review，Test data preparation takes 6 weeks．Design takes 6 weeks and it is followed by development and unit testing，for one module it takes 2 weeks and for the other module it takes 2 weeks．There are no dependencies between modules and they can be developed simultaneously．After test data preparation and development and unit testing of both the modules，there is 2 weeks system testing．What is duration of the critical path ？（）
A．14 week
B．15 week
C．20 week
D．19 week
