Which of the following provides the best example of a product risk leading to a project risk?

A: The signalling systems may have more defects than anticipated, leading to the need for more retesting to be carried out. B: There may be unexpected lags on the network traffic communication, causing drivers to slow the trains down unnecessarily. C: The new development staff may require training for this type of system, which, if not carried out, may lead to an increase in the number of defects introduced. D: The budget may need to be increased significantly during the project, otherwise there may be delays in the delivery of the system.