The specs are totally inadequate to permit any comment. Much more detail and precision is needed.

Here's a really useful set of specs:
https://www.madisoundspeakerstore.com/images/products/830991-specs.jpg

Louis wrote:

I'm building my own 2-way Bookshelf Speaker, and i'm having trouble to choose a woofer because i am very confused about the frequency response, the tweeter is very easy to choose because the frequency response doesn't change, all dome tweeters that i looked at has a fr of 1KHz - 20KHz and that's good but choosing a woofer is hard as hell, so i'm gonna put up 4 woofer specs and tell me which one is the hypothetically the best for 2 way bookshelf speaker, note that these woofers are not sub or mid woofers they are just labeled as woofers and they are all in same sizes (5 inch woofers) and yes these are real woofer specs & i didn't put the model names to avoid confusion

Woofer A fr - 20Hz - 15KHz
Woofer B fr - 100Hz - 7KHz
Woofer C fr - 80Hz - 6KHz
Woofer D fr - 50Hz - 1KHz

So i am very confused because i don't know which one is good to pair with a tweeter with a fr of 1-20khz, I am new to speaker building and i need some advice, and please explain to me why these woofers are in same
sizes but different frequency range, I don't care about the material that it's made of, just imagine the woofers are made with the same materials and which of the four will most likely be good to pair with a tweeter for my 2-way speakers, please give your insights thank you.

What you need is a good book on speaker design, and about 20 hours of study regarding basic speaker design issues.

At this point you seem to know about 10% of what you need to know about building/designing a speaker. You are like a milkman who has wandered into a crematorium and is looking for the cows.

You are not even asking the right questions, and are apparently not aware that the specs on a woofer need to be evaluated in conjunction with data on the enclosure type, size, and other damping issues. A woofer's performance is totally dependent on not only its construction, but the type and size and loading of its enclosure.

So i am very confused...REALLY REALLY CONFUSED

What you need is a good book on speaker design, and about 20 hours of study regarding basic speaker design issues.

RECOMMENDED:

"INTRODUCTION TO LOUDSPEAKER DESIGN" by John L. Murphy

Read this book carefully and you will have some good insights into the principles of speaker design.

If you don't want to take the trouble to get and read the book, you are wasting your time and money.