spf: does the registration domain "include:" also refer to subdomains?

I have a question when setting up my SPF record. I would like to know if I set up an inclusion record in the SPF record it will also "include" the subdomains of that primary domain that I have included.

Let's take a look at an example in my doubt:

Example:

v=spf1 +include:example.com -all

Will this "+ include: example.com" be covered if my email is sent from subdomain1.example.com or subdomain2.example.com ???

I really appreciate your comments.

What is the difference between "include" and "extend" in Ruby?

I'm studying Ruby, and I've realized that there are 2 (maybe more) ways to inject methods into a class. At first I thought it could be the same, since Ruby is a language that claims to be very flexible for programmers.

However, I only attended a class where the teacher explained hook and the methods self.included, self.extended and self.inheritedand made me think: "Do these two ways below really make no difference?
"

Using the include:

class MinhaClasse
    include Modulo
end

Using the extend:

class MinhaClasse
    extend Modulo
end

Is there a difference between using the extend and include ? If so, what is the difference and when should I use each one?