问题：
[单选题]Which of the following statement about defensive programming is incorrect?
AAssertions are mainly used after the release of the product to allow the program to self-check the code at runtime
BIn order to avoid corruption of illegally entered data, we have to check the values of all externally sourced data
CNeed to check the value of all input parameters of the subroutine
DWe can use assertions to prevent errors during the running of the code
