Under the action of load, which of the following is true for reactions and internal forces of statically determinate structure?
选项：

A:It is not only determined by equilibrium condition, but also by deflection condition;
B:It can be obtained by static equilibrium condition, but sometimes the value is uncertain;
C:In special cases, it can be uniquely determined by the static equilibrium condition;
D:All of them can be obtained by static equilibrium condition, and the numerical value can be determined.