Which of the Following Is True About Probable Cause

Which of the following is true about probable cause?

A) Probable cause does not necessarily need to precede the stop or arrest. If the situation is dangerous, the evidence may be obtained after a safe stop and can be used to establish probable cause.
B) An officer can establish probable cause based on his or her own observations.
C) An officer cannot establish probable cause based on something observed by someone else.
D) If evidence is obtained without probable cause, it will likely be okay to use at the time of trial.