阅读理解

    Once Effendi had a joke with the Prime Minister(宰相). He said that the Minister would die the next day. The next day, the Minister fell on to the ground from a horse and really died. When the king learned this, he got angry and sent his men to catch Effendi at once.

    When Effendi was brought to him, the king shouted angrily, "Effendi, since you knew when my Minister would die, you must know the date of your own death. Say it out, or you'll die today."

    Effendi looked at the king for a while. Then he answered, "But how can I know? I'll die two days earlier than you." The king was afraid that if he killed Effendi, he himself would die after that. He thought he must keep Effendi alive as long as possible, so he let Effendi go.

We can surely overcome these difficulties as long as we are________united.

在极坐标系中，圆ρ=2被直线ρsinθ=1截得的弦长为（　　）