Any phenomenon that…………. Can serve as a …………… .

Answer

To solve the fill-in-the-blank question, we need to identify the key terms that fit logically into the sentence structure. The question states: "Any phenomenon that __________ can serve as a __________."

### Step-by-Step Solution:

1. **Identify the first blank**: We need to think of a characteristic or quality of a phenomenon that allows it to serve a purpose. In this case, we can consider phenomena that exhibit regularity or repetition.

- Possible answer for the first blank: "repeats itself."

2. **Identify the second blank**: The second part of the sentence requires a term that describes what the phenomenon can serve as. Since the first part mentions repetition, we can think of terms related to measurement or reference.

- Possible answer for the second blank: "block" (as in a reference block for measurement).

3. **Combine the answers**: Now we can fill in the blanks with our chosen terms.

- Complete sentence: "Any phenomenon that repeats itself can serve as a block."

### Final Answer:
"Any phenomenon that repeats itself can serve as a block."

---