apple 是可数名词，但是在用单双数时看语境而定，如果表达水果的种类不用加s，是不可数的。 但是如果要表达今天买了20个苹果就要加s，表示个数时是可数的。
I want an apple.
我想要一个苹果。
Of course, a number of factors will dictate how long an apple tree can survive
当然，影响一棵苹果树寿命的因素有很多。
The apple was brought over here by the colonists when they came.
苹果是早期殖民地开拓者来的时候带过来的。
The trees were laden with apples.
树上都挂满了苹果。
If you can't find any decent apples, you can always try growing them yourself
如果你找不到像样的苹果，你总还可以试着自己种。
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