Dudes, I need help:

(Fill in da blank)

Place the _apstone atop the completed pyramid.

(its 1 letter)

i don't know what "da blank" means...

Capstone?

Yes, the correct answer is "capstone". To arrive at this answer, you can follow a few steps:

1. Read the sentence carefully to understand the context and the information provided.
2. Identify that you need to fill in the blank with a single letter.
3. Look at the word "Capstone" and notice that it has similar letters to "_apstone".
4. Infer that the missing letter in the blank should be "C" to complete the word "capstone".
5. Place the letter "C" in the blank to form the word "capstone".
6. The final sentence would then be: "Place the capstone atop the completed pyramid."

Remember to carefully analyze the given information, use your understanding of language, and make logical deductions to find the correct answer.