grammar question, please help?

If you want to identify the "Pear and peach" as a group such as "Pen and Paper" then you can use "is" as its verb since that is considered as singular subject, but if you define pear and peach as different entities, thus making them plural subject, then you should be using "are".

second one
it is called principle of proximity

although the sentence is " a pear and hundreds of peach " ,it still use "is"

The second sentence.

here is a pear and peach for you.