Here are the answers based on the position of primary stress:

**Question 1:** After marriage, Mrs. Hoa always keeps a good _____ with her mother-in-law.
A. association (stress is on the third syllable)
B. relation (stress is on the second syllable)
C. friendship (stress is on the first syllable)
D. relationship (stress is on the third syllable)
**Answer: C** (friendship differs in stress)

**Question 2:** His choice of future career is quite similar___________mine.
A. for
B. to
C. with
D. at
**Answer: A** (for is stressed differently)

**Question 3:** A university degree is considered to be a _________for entry into most professions.
A. claim (stress is on the first syllable)
B. demand (stress is on the second syllable)
C. requisite (stress is on the first syllable)
D. request (stress is on the second syllable)
**Answer: C** (requisite differs in stress)

**Question 4:** Don’t forget to ring me up if _________ any changes in the timetable.
A. they are
B. it will be
C. there will be
D. there are
**Answer: B** (it will be differs in stress)

**Question 5:** The athlete failed in his last____________to break the world record.
A. attempt (stress is on the second syllable)
B. trial (stress is on the first syllable)
C. effort (stress is on the first syllable)
D. experiments (stress is on the second syllable)
**Answer: B** (trial differs in stress)

So, the letters for the answers are:
1. C
2. A
3. C
4. B
5. B