放寒假的时候，小明去了哈尔滨滑雪，小刘则去了海南岛的三亚领略海岛风情，下面是他们拍摄的两幅照片，你认为造成两地气候差异的最主要因素是（　　）

城市中最广泛的土地利用方式是（   ）

如图甲所示，Q₁、Q₂为两个被固定的点电荷，a、b是它们连线的延长线上的两点．现有一带负电的粒子只在电场力作用下以一定的初速度从a点开始经b点向远处运动，粒子经过a、b两点时的速度分别为v_a、v_b，其速度时间图象如图乙所示．下列说法正确的是（   ）

Dear Simon,

    How are you? Last week I ____ to Xi'an. It's in the northwest of China. I went there ____ plane. The plane took us to the ____. First, I was a little  ____. Then I looked out of the window.

The plane was above the ____. I ____ some mountains below. I ____ lunch on the plane. Later I arrived in Xi'an. I ____ many interesting places. The trip was great!

Love,

Daming