To inform my audience of three major theories about how the great pyramid of giza was built is an example of a specific purpose statement for an informative speech about

A concept.

Explanation:

There are four major categories of informative speeches, defined after the main focus of a speech.

Informative speeches could be about:

This particular informative speech would be about a concept.

Concepts in informative speeches are whatever is considered more abstract, as they deal with rather abstract topics such as theories, ideas and beliefs.

Here we have theories about how the Great Pyramid of Giza was built so it is safe to say this informative speech would be about a concept.

the sentence that contains a restrictive clause is a.they decided to meet where the band was performing

explanation:

a restrictive clause is also known as an essential clause