Here are the words where the main stress pattern differs from the others:

1. **A. champion** (stress on the first syllable) - **C. factory** (stress on the first syllable)
2. **A. illustrate** (stress on the first syllable) - **B. action** (stress on the first syllable)
3. **A. explanation** (stress on the third syllable) - **B. experiment** (stress on the second syllable)
4. **A. photography** (stress on the second syllable) - **C. mathematical** (stress on the third syllable)
5. **C. industry** (stress on the first syllable) - **D. result** (stress on the second syllable)

In summary, the words with different main stress patterns are:
1. No difference identified.
2. No difference identified.
3. **A. explanation**
4. **A. photography**
5. **D. result**