singular, plural or either

[beachboy]

My favorite (favourite) fruit is
- grape or grapes?
- apple or apples?
- watermelon or watermelons?

 

[cclaff]

My favorite (favourite) fruit is
- grape or grapes?
- apple or apples?
- watermelon or watermelons?

Because of the problem I would say:
Grapes are my favorite fruit.
Apples are my favorite fruit.
Etc.

 

[RonBee]

My favorite fruit is

grapes
apples
watermelon
​

(The word fruit is the subject is the subject and is construed as singular.)



On the other hand:

Watermelon is my favorite fruit.
Apples are my favorite fruit.
Grapes are my favorite fruit.
​

~R

 

[beachboy]

Oh, thanks! Just one more question: what do I have to consider before I choose between the singular (watermelon) or the plural (grapes)? The size?