a lot of+可数/不可数名词,fruit既是可数名词又是不可数名词。
做可数名词表示水果的种类。a lot of fruit意为很多水果,强调的是整体的许多,这里fruit当集合名词讲,不可数。 
a lot of fruit的'例句:
He bought a lot of fruit such as apples and peaches.他买了许多水果,如苹果、桃子等等。
I eat a lot of fruit anyway.总之我吃了大量的水果。
He also eats a lot of fruit他也吃大量的水果。
The basket contains a lot of fruit.筐里有很多水果。
We get a lot of fruit from South Africa.我们从南非进口了许多水果。