| a+b | & gt； In the case of 1, when the angle θ is 120 degrees, it is easy to get |a+b|= 1, so we can know that the angle θ belongs to [0,2 π/3], that is, p 1 holds.

|a-b| > In the case of 1, when the angle θ is 60 degrees, it is easy to get |a-b|= 1, so we can know that the angle θ belongs to [π/3, π], that is, p4 holds.

To sum up, choose a for this question.

Question 1 1 Answer next time.