草履虫的排泄是通过下列哪些结构来完成的（   ）

Dear Mr. Wang,

    Someone comes to the office to see you in the morning, but you and your wife are out. He comes here at 10am. Because he is very busy, he goes away half an hour later. He tells me that he is your classmate at college(大学). Now he teaches Chinese in a high school(高中) in this city and he lives near the No. 6 Middle School. He is a very tall man with short hair. He wears a pair of glasses. He tells me his telephone number is 33426685. He is often at home at 7:00 pm. So you can call him in the evening.

如图，在M、N处固定两个等量同种点电荷，两电荷均带正电．O点是MN连线的中点，直线PQ是MN的中垂线．现有一带正电的试探电荷q自O点以大小是v₀的初速度沿直线向Q点运动．若试探电荷q只受M、N处两电荷的电场力作用，则下列说法正确的是（   ）

（1﹣2x）⁴展开式中含x项的系数（　　）