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

2015年诺贝尔生理学或医学奖获得者屠呦呦，早年从中医古籍里得到启发，通过对提取方法的改进，首先发现中药青蒿的提取物有高效抑制疟原虫的成分。这一发现在抗疟疾新药青蒿素的研发过程中起到关键性的作用。青蒿素的研发过程说明（   ）。

①创新推动了社会生产力的发展

②辩证的否定是联系的环节，也是发展的环节

③充分发挥主观能动性是科学研究取得成功的前提

④应坚持开拓创新，在实践中检验真理和发展真理

    Mr. Black takes his daughter 1 a restaurant. They sit down, and there are a lot of  2 in the restaurant. They 3 for a long time, but no waiters come to their table.

    Mr. Black says, "I'm 4, I can't wait." He waits for a minute and says, "Now I am going to 5 something to get a waiter soon."

    He goes out of the restaurant and 6 the restaurant, "My 7is at a table in your restaurant, she 8 a red hat."

    The waiter finds the girl and he says to Mr. Black, "Yes, she's here. Do you want to 9 her?"

    "No," says Mr. Black, "But please give her something to eat quickly. She is very 10". Then he goes back to the restaurant. He is glad to see that a waiter is now at this table.

①在BC上找一点P，使点P到AB和AC的距离相等；

②在射线AP上找一点Q，使QB=QC．