俄罗斯被称为世界的“世界的加油站”，石油和天然气的运输方式主要是（    ）

增加：在缺词处加一个漏字符号( )，并在其下面写出该加的词。

删除：把多余的词用(＼)划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

Dear Jack,

    Next Saturday will my birthday. I'm going to hold a birthday party at home on the evening. It will start at 7:30. Some classmates as good as some foreign friends have been invited. The activities include singing, dancing and sharing interesting experiences. Surely, we'll have a good time. I would feel honoring if you could come. I live at 656 Minzu Street. You can take Bus No. 11 or No. 15 and got off at the stop of Guang Ming High School. Justly on the opposite side is my house, what is red with a white door. I'm sure of you can't miss it. I do hope they will come.

    Best wish.

Yours,

LiHua

在正四棱锥S﹣ABCD中，O为顶点在底面内的投影，P为侧棱SD的中点，且SO=OD，则直线BC与平面PAC的夹角是（　　）

“约索夫森结”由超导体和绝缘体制成．若在结两端加恒定电压U，则它会辐射频率为ν的电磁波，且ν与U成正比，即ν=kU．已知比例系数k仅与元电荷e的2倍和普朗克常量h有关．你可能不了解此现象的机理，但仍可运用物理学中常用的方法，推理判断比例系数k的值可能为____.