Most can easily be made longer (try adding " She said that… " to the beginning of any declarative sentence).

大多数都可以很容易地变长(试着在陈述句的开头加上“She said that… ”)。

So a declarative sentence is a statement. Just straight up.

所以陈述句是陈述句。直接起来。

And other short declarative sentences in the story create a mix of breathless speed and weighty pauses.

故事中的其他简短陈述句混合了令人窒息的速度和沉重的停顿。

It's a declarative sentence. If I say, " He seems nice" , is he nice? Maybe, but probably.

是陈述句。 如果我说，“他看起来很好” ，他很好吗？ 也许吧，但大概吧。