Being happy is a skill that can be learned like a foreign language, and one way to ______ ourselves to be happy is to write down the little things that cheer us up each day.

-- Whose is this sweater?

--            

在同一平面内，两直线的位置关系必是（  ）

①地球各地出现极光现象      ②地球磁针不能正确指示方向

③固定电话将受到干扰         ④高纬度地区会出现极昼现象．