Sure! Here are the answers to your questions:

### Question 1: Pronunciation
1. **A. anthem** - pronounced /ˈæn.θəm/
2. **B. breathless** - pronounced /ˈbrɛθ.ləs/
3. **C. although** - pronounced /ɔːlˈðoʊ/
4. **D. thrilling** - pronounced /ˈθrɪl.ɪŋ/

**Answer: A. anthem** (the "th" sound differs from the others)

5. **A. principal** - pronounced /ˈprɪn.sɪ.pəl/
6. **B. optimal** - pronounced /ˈɒp.tɪ.məl/
7. **C. rural** - pronounced /ˈrʊə.rəl/
8. **D. salmon** - pronounced /ˈsæm.ən/

**Answer: C. rural** (the "r" and "u" sounds differ from the others)

### Question 2: Primary Stress
1. **A. fantasy** - stress on the first syllable: **FAN**-tasy
2. **B. convincing** - stress on the second syllable: con-**VINC**-ing
3. **C. concentrate** - stress on the first syllable: **CON**-centrate
4. **D. conference** - stress on the first syllable: **CON**-ference

**Answer: B. convincing** (the stress is on the second syllable, while the others are on the first)

5. **A. dimension** - stress on the second syllable: di-**MEN**-sion
6. **B. responsible** - stress on the third syllable: re-**SPON**-sible
7. **C. piracy** - stress on the first syllable: **PI**-racy
8. **D. effective** - stress on the second syllable: ef-**FEC**-tive

**Answer: C. piracy** (the stress is on the first syllable, while the others have stress on different syllables)

I hope this helps!