[填空题]
下面的短文后有2项测试任务：
(1)第23-26题要求从所给的6个选项中为第1-4段每段选择1个最佳标题；
(2)第27-30题要求从所给的6个选项中为每个句子确定1个最佳选项。

Icebergs

1 Icebergs are among nature’s most spectacular(壮观的) creations, and yet most people have never seen one. A vague air of mystery envelops them. They come into being—somewhere—in faraway, frigid waters, amid thunderous noise and splashing turbulence, which in most case no one hears or sees. They exist only a short time and then slowly waste away(消融) just as unnoticed.
2 Objects of sheerest(最纯粹的) beauty they have been called. Appearing in an endless variety of shapes, they may be dazzlingly white, or they may be glassy blue, green or purple, tinted faintly or in darker hues. They are graceful, stately, inspiring—in calm, sunlight seas.
3 But they are also called frightening and dangerous, and that they are—in the night, in the fog, and in storms. Even in clear weather one is wise to st